Controlled/modified release oral methylphenidate formulations

ABSTRACT

The invention is directed to oral modified/controlled release methylphenidate formulations which provide a rapid initial onset of effect and a prolonged duration of effect. Preferably, the peak concentration is lower than that provided by the reference standard for immediate release methylphenidate formulations, and the duration of effect falls rapidly at the end of the dosing interval so as not to affect the appetite of the patient at dinner nor the patient&#39;s sleep thereafter.

This application is a continuation of U.S. patent application Ser. No.09/465,158, filed Dec. 16, 1999, now U.S. Pat. No. 6,673,367 whichclaims the benefit of U.S. Provisional Application No. 60/112,667, filedDec. 17, 1998, the disclosure of which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

Sustained release dosage forms are central in the search for improvedtherapy, both through improved patient compliance and decreasedincidences of adverse drug reactions. It is the intent of all sustainedrelease formulations to provide a longer period of pharmacologic actionafter administration than is ordinarily obtained after administration ofimmediate-release dosage forms. Sustained release compositions may beused to delay absorption of a medicament until it has reached certainportions of the alimentary tract, and maintain a desired concentrationof said medicament in the blood stream for a longer duration than wouldoccur if conventional rapid release dosage forms are administered. Suchlonger periods of response provide for many therapeutic benefits thatare not achieved with corresponding short acting, immediate releasepreparations. Thus, therapy may be continued without interrupting thesleep of the patient, which is of special importance, for example, whentreating a patient for moderate to severe pain (e.g., a post-surgerypatient, a cancer patient, etc.), or for those patients who experiencemigraine headaches on awakening, as well as for the debilitated patientfor whom sleep is essential. A further general advantage of longeracting drug preparations is improved patient compliance resulting fromthe avoidance of missed doses through patient forgetfulness.

Unless conventional rapid acting drug therapy is carefully administeredat frequent intervals to maintain effective steady state blood levels ofthe drug, peaks and valleys in the blood level of the active drug occursbecause of the rapid absorption, systemic excretion of the compound andthrough metabolic inactivation, thereby producing special problems inmaintenance therapy of the patient. In view of this, it is considered agoal of many skilled in the art that a controlled release dosage formwill ideally provide therapeutic concentration of the drug in blood thatis maintained throughout the dosing interval with a reduction in thepeak/trough concentration ratio. Central to the development process arethe many variables that influence the in vivo release and subsequentabsorption of the active ingredients from the gastrointestinal tract.

It is known in the pharmaceutical art to prepare compositions whichprovide for sustained release of pharmacologically active substancescontained in the compositions after oral administration to humans andanimals. Sustained release formulations known in the art includespecially coated pellets, coated tablets and capsules, and ion exchangeresins, wherein the slow release of the active medicament is broughtabout through selective breakdown of the coating of the preparation orthrough compounding with a special matrix to affect the release of adrug. Some sustained release formulations provide for related sequentialrelease of a single dose of an active compound at predetermined periodsafter administration.

While controlled and/or sustained release compositions have constituteda definite advance in the art, improvements in these compositions havebeen sought, particularly for preparations available for conditions suchas Attention Deficit Hyperactivity Disorder (ADHD), diabetes etc.

Attention Deficit Disorders are the most common psychiatric disorders inchildren (Campbell et al. 1992) with reported rates ranging from 4% to9% (Aman et al. 1983). Attention Deficit Disorder (ADD) is characterizedby inattention and impulsivity and may be present with hyperactivity(ADHD) (Shaywitz et al. 1984). Other characteristics may includeaggressiveness, stealing, lying, truancy, setting fires, running away,explosiveness, cognitive and learning problems as well as poor socialskills (Campbell et al. 1992). It is four to five times more frequent inboys than girls (Campbell et al. 1992).

Stimulant medication, such as amphetamines, have been shown to be themost effective agents in the treatment of children with disorders ofactivity modulation and attention regulation and result in significantimprovement in 70 to 80 percent of affected children (Shaywitz et al.1984). Positive effects of stimulants have been documented in a varietyof areas including behavioral, social, perceptual performance, motoractivity, impulse control, attention regulation and cognitiveperformance (Barkley 1977, Kavale 1983, Offenbacher et al. 1983,Rosenthal et al 1978).

Methylphenidate {dl-threo-methyl-2-phenyl-2-(2-piperidyl)acetate} is thepsychostimulant used most frequently in the treatment of hyperactivityand attention deficit disorder. It appears to have a higher incidence ofpositive effects and a lower incidence of adverse effects than otherpsychostimulants. The efficacy of methylphenidate (“MPH”) in improvingattention and behavioral symptoms has been supported by many studies.

Immediate release methylphenidate preparations, because of their shorthalf-life, require frequent administration at short intervals to ensureadequate treatment throughout a child's school day. The rapid onset andoffset of immediate release methylphenidate preparations means that amedicated child with attention deficit disorder will be maximallyaffected only for relatively brief periods during the day. Due to itsshort half-life, MPH is usually given twice per day, usually once afterbreakfast and once during the school day, an event that some childrenand some school personnel apparently avoid, resulting in poor compliancewith prescribed regimens (Brown et al., 1985; Firestone 1982).Compliance is a major problem for children who require a midday ormidafternoon dose as many schools prohibit children from takingmedications during the school day and others often insist that allmedications be given by a nurse. Poor compliance in taking medicationmay explain, in part, the variable and conflicting results reported inmany studies of the effect of medication on improving the behavior ofhyperactive children. These limitations of immediate releasemethylphenidate led to interest in products with longer effectiveperiods of action. These limitations of immediate releasemethylphenidate preparations led to interest in products with longereffective periods of action.

A sustained release form of methylphenidate (Ritalin® SR) iscommercially available. As a result of many clinical trials, variousopinion leaders in treatment of attention deficit hyperactivity disorderhave made the following comments regarding Ritalin® SR (sustainedrelease methylphenidate) produced by Ciba-Geigy: (i) Ritalin® SR doesnot have a sufficiently early onset of effect to allow for behavioralmanagement in the early morning; (ii) Ritalin® SR does not have thebeneficial late effects that would be produced by a lunch time dose ofimmediate release methylphenidate, thus defeating the purpose of usingan SR formulation; (iii) The effects of Ritalin® SR are inconsistent orerratic over the course of the day.

There is a need in the art to develop drug formulations which provide arapid onset, a prolonged action, followed by rapid offset of effect inorder to overcome the deficiencies of the current state of the art.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide new oral dosageformulations of methylphenidate or similarly acting drugs which resultsin improved patient compliance.

It is an object of the present invention to provide new oral dosageformulations which represent improvements over currently availablepreparations available for conditions such as Attention DeficitHyperactivity Disorder (ADHD).

It is an object of the present invention to provide new oral dosageformulations of methylphenidate or similarly acting drugs which ensureadequate treatment throughout a child's school day.

It is an object of the present invention to provide new oral dosageformulations which allow a child with attention deficit disorder to bemaximally treated throughout the daytime, while being administered onlyonce, i.e., in the morning.

It is a further object of the present invention to provide newcontrolled/modified release oral dosage formulations which provide arapid onset and rapid offset with an extended release of activemedicaments incorporated therein.

It is yet another object of the present invention to provide newcontrolled/modified release oral dosage formulations which are useful inall types of pharmaceutically active ingredients and which can extendthe time of release of all such ingredients.

It is yet another object of the present invention to provide an oralcontrolled release formulation which combines both a rapid onset andsustained plasma concentrations throughout the day.

It is yet another object of the present invention to provide a“multi-layer release” (MLR) technology which is useful for all types ofpharmaceutically active ingredients and which can extend the duration ofaction for a desired length of time.

To address the above-mentioned deficiencies as well as other goals, thepresent invention is directed in part to a controlled release productwhich is intended to combined both a rapid onset and sustained plasmaconcentrations throughout the day. Significantly, the formulations ofthe present invention provide a rapid onset, a prolonged action,followed by rapid offset of effect, i.e., a “square wave” profile.

In accordance with the above objects and others, the present inventionis directed in part to an oral dosage form comprising an effectiveamount of methylphenidate or a pharmaceutically acceptable salt thereofand at least one release modifying material which causes the formulationto provide a time to maximum plasma concentration at about 0.5 to about4 hours after oral administration, a peak plasma concentration fromabout 3 ng/ml to about 6.5 ng/ml per 20 mg dose of methylphenidatecontained in the oral dosage form, wherein the peak plasma concentrationis from about 1.0 to about 2.0 times the plasma concentration ofmethylphenidate provided by the formulation at about 9 hours after oraladministration, and wherein the duration of effect provided by themethylphenidate contained in the formulation falls below effectiveplasma concentrations at about 8 to about 12 hours after oraladministration. In certain preferred embodiments, the oral dosage formprovides a time to maximum plasma concentration at about 0.5 to about 2hours after oral administration. In certain further preferredembodiments, the peak plasma concentration is from about 1.0 to about1.7 times the plasma concentration of methylphenidate provided by theoral dosage form at about 9 hours after oral administration. In certainfurther preferred embodiments, the duration of effect provided by themethylphenidate contained in the oral dosage form falls below effectiveplasma concentrations at about 8 to about 10 hours after oraladministration.

In certain further preferred embodiments, the formulation provides atime to maximum plasma concentration at about 0.5 to about 4 hours afteroral administration and provides effective blood levels for at leastabout 6 hours after administration.

In certain further preferred embodiments, the formulation exhibits a“plateau” in the blood plasma curve which lasts from about 2 hours toabout 6 hours. Other embodiments exhibit a “plateau” which lasts fromabout 6 hours to about 12 hours. The “plateau” is characterized by astabilized plasma concentration, wherein the plasma level at the end ofthe measured interval does not differ by more than 20%, preferably by nomore than 10% of the plasma concentration at the beginning of themeasured interval.

In certain further preferred embodiments, the formulation exhibits abimodal release of active agent from the dosage form. Bimodal release ofthe active agent is characterized by the active agent being release fromthe dosage form by more than one distinct release rate. In someembodiments, the release rates can be separated by a no-release or asubstantially no-release interval, although this is not alwaysnecessary.

In certain further preferred embodiments, the formulation exhibits abiphasic absorption of the active agent. Biphasic absorption of theactive agent is characterized by the active agent being absorbed througha natural barrier (e.g. the mucosal lining of the gastro-intestinaltract) by more than one distinct absorption rate. In some embodiments,the absorption rates can be separated by a no-absorption or asubstantially no-absorption interval, although this is not alwaysnecessary. A formulation can exhibit both biphasic absorption andbimodal release of the active agent, with the biphasic absorption beinga function of the bimodal release rate. However, biphasic absorption isnot always attributed to release rate and can occur in a formulation notexhibiting bimodal release.

In preferred embodiments the formulation exhibits bimodal release and/orbiphasic absorption to provide a “plateau” in the blood plasma curvewhich lasts from about 2 hours to about 6 hours. Other embodimentsexhibit bimodal release and/or biphasic absorption to provide a“plateau” which lasts from about 6 hours to about 12 hours. Otherembodiments, maintain effective plasma levels of the active agent forabout 16 to about 18 hours after administration of the dosage form.

The present invention is further directed to an oral dosage formcomprising an effective amount of methylphenidate or a pharmaceuticallyacceptable salt thereof and at least one release modifying materialwhich causes the formulation to provide a in-vitro dissolution of thedrug of from about 0 to about 45% released after 0.25 hour; from about10 to about 50% released after about 1 hour; from about 30 to about 80%drug released after about 4 hours; not less than about 65% drug releasedafter 8 hours; and not less than about 80% of the drug released afterabout 12 hours; the oral dosage form when orally administered to a humanpatient further providing a time to maximum plasma concentration atabout 0.5 to about 2 hours after oral administration, and a duration ofeffect which lasts from about 8 to about 10 hours after oraladministration, wherein the plasma concentration of the drug rapidlyfalls at about 8 to about 10 hours after oral administration to a levelwhich is below the minimum effective plasma concentration. In certainpreferred embodiments, the oral dosage form, when orally administered toa human patient, provides a peak plasma concentration from about 4 ng/mlto about 6.5 ng/ml per 20 mg dose of methylphenidate contained in theoral dosage form. In certain preferred embodiments, the oral dosageform, when orally administered, provides a peak plasma concentrationfrom about 5 ng/ml to about 6.5 ng/ml per 20 mg dose of methylphenidatecontained in the oral dosage form. In certain further preferredembodiments, the oral dosage form provides peak plasma concentrationfrom about 1.0 to about 2.0 times the plasma concentration ofmethylphenidate provided by the formulation at about 9 hours after oraladministration, and more preferably from about 1.0 to about 1.7 timesthe plasma concentration of methylphenidate provided by the formulationat about 9 hours after oral administration.

With respect to the drug methylphenidate and ADHD, the benefits of thenew formulations described herein include: a) the ability to obviate theneed for a lunch-time dose at school and b) an onset of drug effectwhich is equivalent to that of an immediate release methylphenidateformulation; and c) the duration of action extending beyond the schoolday, i.e., a duration of effective blood levels of 10–12 hours.

In certain embodiments of the invention, the controlled/modified releaseformulation is based on a multi-layered release (“MLR”) technology, andthe drug product can be in an oral capsule containing beads. In the caseof beads, encapsulated in a capsule, each bead contains a series oflayers with different characteristics—an outer immediate release layer,a release delaying layer (enteric coat), a controlled release layer overan immediate release layer. The MLR formulation is designed such thatupon oral administration, the formulation provides a rapid dissolutionand absorption of the outer layer of the formulation which contains aportion of the drug in immediate release form, thereby resulting in arapid rise of the drug to therapeutic plasma levels. This is followed bya period of no absorption (due to an enteric coating), followedthereafter by a controlled release of the drug from the formulation tomaintain plasma levels. After absorption of the drug from an immediaterelease core, plasma levels then rapidly decrease. By virtue of therelease of the drug from the MLR formulation, the plasma level of thedrug, when plotted on a time/concentration curve, takes the appearanceof a “square wave”.

In certain preferred embodiments, an acrylic resin is utilized toprovide the controlled slow release of therapeutically activeingredients over a predetermined or a specified period of time, theacrylic resin thereby comprising a significant part of the “basecomposition”. Base compositions prepared from such acrylic resinsprovide sustained release of therapeutically active ingredients over aperiod of time from five hours and for as much as 24 hours afteradministration, generally oral administration, in humans or animals.

In other embodiments of the invention, the formulations of the inventionare composed of:

-   (i) a mixture of immediate release particles (e.g., beads) and    enteric coated immediate release particles (e.g., beads); (ii) a    mixture of immediate release particles (e.g., beads) and enteric    coated controlled release particles (e.g., beads) or (iii) a mixture    of immediate release particles (e.g., beads) and controlled release    particles (e.g., beads). In each such instance, the mixture of    particles possessing different release properties are blended    together and filled into hard gelatin capsules.

In certain preferred embodiments, the controlled/modified releasemethylphenidate formulations of the invention consist of a plurality ofsingle beads, each containing an immediate-release component incombination with an enteric coated controlled-release component toproduce a delay in the absorption process. The drug product is an oralcapsule containing methylphenidate beads. Each bead contains a series oflayers with different release characteristics—an outer immediate releaselayer; a release delaying layer; a controlled release layer; and animmediate release core. The final product is a capsule containingmulti-layer release (MLR) beads which have both immediate release andcontrolled release components. It is made up of a controlled releasebead which is enteric coated to delay dissolution until after gastricemptying. The enteric coated controlled release bead has an immediaterelease topcoat to provide an initial rate of absorption equal to orgreater than Ritalin immediate release tablets. The immediate releasecomponent represents 40% of the total dose per bead and the controlledrelease component represents 60%. This formulation is designed toproduce a rapid rise to therapeutic plasma levels after oraladministration, due to the rapid dissolution and absorption of the outerlayer, followed by a period of reduced absorption and then controlledrelease of the immediate release core, to maintain therapeutic plasmalevels. After absorption of the immediate release core, plasma levelswould then rapidly decrease according to the elimination kinetics ofmethylphenidate. The results of a bioavailability study of thisformulation indicate a biphasic release profile that is consistent withthe pharmaceutical rationale discussed herein.

In other embodiments of the invention, the bead size of the formulationscan be adjusted in order to obtain a desired pharmacokinetic profilebased on the correlation between gastric emptying and bead size. Asmaller bead size exhibits faster gastric emptying as compared to alarger bead size.

Other objects and advantages of the present invention will be apparentfrom the further reading of the specification and of the appendedclaims.

The term “pH-dependent” for purposes of the present invention is definedas having characteristics (e.g. dissolution) which vary according toenvironmental pH (e.g., due to changes in the in-vitro dissolutionmedia, or due to passage of the dosage form through the gastrointestinaltract.

The term “pH-independent” for purposes of the present invention isdefined as having characteristics (e.g., dissolution) which aresubstantially unaffected by pH, in that a difference, at any given time,between an amount of methylphenidate released at one pH and an amountreleased at any other pH, when measured in-vitro using the USP PaddleMethod of U.S. Pharmacopeia XXII (1990) at 100 rpm in 900 ml aqueousbuffer, is no greater than 10%.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of embodiments of the inventionand are not meant to limit the scope of the invention as encompassed bythe claims.

FIG. 1 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Formulation 1 andRitalin® as a function of time when given under fasting conditions.

FIG. 2 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Formulation 1 andRitalin® as a function of time when given under fed conditions.

FIG. 3 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Formulation 1 as afunction of time when given under fasting and fed conditions.

FIG. 4 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Ritalin® as afunction of time when given under fasting and fed conditions.

FIG. 5 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Formulation 2 underfasting and fed conditions, and Ritalin® SR under fasting conditions, asa function of time.

FIG. 6 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Formulation 3 underfasting and fed conditions, and Ritalin® SR under fasting conditions, asa function of time.

FIG. 7 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Formulations 2 and 3under fasting conditions as a function of time.

FIG. 8 is a graphical comparison of the mean plasma concentration ofmethylphenidate when test subjects are treated with Formulations 2 and 3under fed conditions as a function of time.

FIG. 9 a graphical representation of one target plasma drugconcentration profile in accordance with the invention.

FIG. 10 is a graphical representation of the correlation of the in-vitrodrug dissolution profile with the in-vivo absorption profile ofFormulation 1.

FIG. 11 is a graphical representation of a target absorption profile ofa formulation in accordance with the invention.

DETAILED DESCRIPTION

Methylphenidate (2-Piperidineacetic acid, α-phenyl-, methyl ester) is apiperidine derivative that is structurally related to amphetamine, andis commercially available in the form of the hydrochloride salt.Methylphenidate is the psychostimulant used most frequently in thetreatment of hyperactivity and attention deficit disorder. It appears tohave a higher incidence of positive effects and a lower incidence ofadverse effects than other psychostimulants. The controlled/modifiedrelease methylphenidate formulations of the invention are thought to actby increasing extracellular dopamine and norepinephrine with thepresumed mechanism of action being uptake block at the nerve terminaltransporters.

The pharmacological properties of methylphenidate are essentially thesame as the amphetamines. However, in contrast to amphetamines,methylphenidate is a mild CNS stimulant with more prominent effects onmental than motor activities. Methylphenidate contains erythro and threoisomers. Locomotor stimulant action is specific to stereo-structure,whereas monoamine oxidase inhibition is not. It has been speculated thatthe mechanism of locomotor stimulant action of methylphenidate may beother than the inhibition of monoamine oxidase. Studies suggest thatsynaptic inhibition of catecholamine uptake by d-threo methylphenidatemay be involved fundamentally in behavioral and pressor effects of theracemic drug. Methylphenidate promotes a dose-dependent behavioralprofile that is very comparable to that of amphetamine. Amphetamineincreases extracellular norepinephrine and serotonin in addition to itseffects on dopamine. Recently work indicates that acute methylphenidateadministration increases extracellular dopamine and norepinephrine,consistent with its presumed mechanism of action as a uptake blocker ofthe nerve terminal transporters.

Peak blood levels following the administration of methylphenidate havebeen noted at 1 to 3 hours (Faraj et al., 1974; Milberg et al., 1975).The half-life of the drug ranges from 2 to 4 hours (Faraj et al., 1974;Hungund et al., 1979; Soldin et al., 1979) in adults and children.Hungund et al. (1979) reported on the pharmacokinetics ofmethylphenidate in four hyperkinetic children. The mean half-life was2.5 hours. Although there was little variability in this parameter, bodyclearance varied by a factor of three. This suggested that plasmamethylphenidate levels are subject to a considerable degree ofinter-patient variability.

The primary route of metabolism for methylphenidate is de-esterificationto ritalinic acid, which accounts for 75% to 91% of total urinarymethylphenidate. Other metabolic products arise from p-hydroxylation oroxidation to the lactam.

The methylphenidate formulations of the present invention may beadministered to children 6 years and over, and preferably have aduration of action from about 8 to about 12 hours, preferably from about8 to about 10 hours. The inventive methylphenidate formulation should betaken at breakfast time and is designed to replace two separate doses ofmethylphenidate immediate release given at breakfast and lunch time.Patients who require more frequent administration of immediate releasemethylphenidate than twice daily may be given an additional dose ofimmediate release methylphenidate at suppertime, when receiving theinventive methylphenidate formulation. The contents of theMethylphenidate MLR capsules may be sprinkled on soft foods beforeadministration.

The controlled/modified release preparations of the present inventionmay be used in conjunction with any multiparticulate system, such asgranules, spheroids, beads, pellets, ion-exchange resin beads, and othermultiparticulate systems in order to obtain a desired sustained-releaseof the therapeutically active agent. Beads, granules, spheroids, orpellets, etc., prepared in accordance with the present invention can bepresented in a capsule or in any other suitable unit dosage form. Anamount of the multiparticulates effective to provide the desired dose ofdrug over time may be placed in a capsule, may be contained in a packetand sprinkled onto food, or may be incorporated in any other suitableoral solid form, such as a tablet. On the other hand, the presentinvention can be in the form of a matrix tablet. With respect to allsuch optional formulations, it is desired that the formulation beprepared such that an initial immediate release of drug provides anearly onset of effect, which onset is analogous to an immediate releaseformulation, and that the formulation further provide a sustainedrelease component which maintains therapeutically effective levels ofthe drug in the plasma for the desired amount of time, followed by arelatively rapid drop-off in blood plasma levels relative to typicalsustained release formulations. Viewed as an in vivo time/concentrationplot, the plasma level of the drug from the formulations of the presentinvention have the appearance of a “square wave”. The immediate releasecomponent preferably represents from about 30% to about 40% of the totaldose and the controlled release component preferably represents fromabout 60% to about 70% of the total dose of methylphenidate contained inthe formulations of the present invention. In certain preferredembodiments, including the MLR embodiments of the invention, theimmediate release component represents about 40% of the total dose andthe controlled release component represents about 60% of the total doseof methylphenidate contained in the formulation.

In the case of methylphenidate, it is desired that the onset of actionoccurs from about 0.5 to about 4 hours, and preferably from about 0.5 toabout 2 hours after the oral dosage form is administered, and it isfurther desired that the dosage form no longer provides effective plasmalevels of methylphenidate from about 8 to about 12, more preferably fromabout 8 to about 10 hours, after oral administration of the dose. Inthis manner, the dose of methylphenidate can be administered to a childin the morning before school begins, provides the desired effect at thestart of the school day, with the pharmacologic action of the drug notwaning until after the school day ends, and preferably before dinner sothat the drug does not have the side effect of acting as an appetitesuppressant.

The formulations of the present invention are designed to produce arapid rise to therapeutic plasma levels after oral administration, dueto the rapid dissolution and absorption of the outer layer, followed bya period of reduced absorption and then controlled release of theimmediate release core, to maintain therapeutic plasma levels. Afterabsorption of the immediate release core, plasma levels would thenrapidly decrease according to the elimination kinetics ofmethylphenidate.

It is generally recognized that the mere presence of an active substancein the gastrointestinal fluids does not, by itself, insurebioavailability. Bioavailability, in a more meaningful sense, is thedegree, or amount, to which a drug substance is absorbed into thesystemic circulation in order to be available to a target tissue site.To be absorbed, an active drug substance must be in a solution. The timerequired for a given proportion of an active drug substance contained ina dosage unit to enter into solution in appropriate physiological fluidsis known as the dissolution time. The dissolution time for an activesubstance from a dosage unit is determined as the proportion of theamount of active drug substance released from the dosage unit over aspecified time by a test method conducted under standardized conditions.The physiological fluids of the gastrointestinal tract are the media fordetermining dissolution time. The present state of the art dissolutiontime for pharmaceutical compositions, and these test procedures aredescribed in official compendia world wide.

Although there are many diverse factors which influence the dissolutionof a drug substance from its carrier, the dissolution time determinedfor a pharmacologically active substance from a specific composition isrelatively constant and reproducible. Among the different factorsaffecting the dissolution time are the surface area of the drugsubstance presented to the dissolution solvent medium, the pH of thesolution, the solubility of the substance in the specific solventmedium, and the driving forces of the saturation concentration ofdissolved materials in the solvent medium. Thus, the dissolutionconcentration of an active drug substance is dynamically modified inthis steady state as components are removed from the dissolution mediumthrough absorption across the tissue site. Under physiologicalconditions, the saturation level of the dissolved materials isreplenished from the dosage form reserve to maintain a relativelyuniform and constant dissolution concentration in the solvent medium,providing for a steady state absorption.

The transport across a tissue absorption site in the gastrointestinaltract is influenced by the Donnan osmotic equilibrium forces on bothsides of the membrane, since the direction of the driving force is thedifference between the concentrations of active substance on either sideof the membrane, i.e. the amount dissolved in the gastrointestinalfluids and the amount present in the blood. Since the blood levels areconstantly being modified by dilution, circulatory changes, tissuestorage, metabolic conversion and systemic excretion, the flow of activematerials is directed from the gastrointestinal tract into the bloodstream.

Notwithstanding the diverse factors influencing both dissolution andabsorption of a drug substance, in many cases an important correlationcan be established between the in vitro dissolution time determined fora dosage form and the in vivo bioavailability. This correlation is sofirmly established in the art that dissolution time has become generallydescriptive of bioavailability potential for many classes of activecomponents contained in a particular dosage form. In view of thisrelationship, the dissolution time determined for a composition is oneof the important fundamental characteristics for consideration whenevaluating whether a controlled release formation should be tested invivo.

With the above in mind, the in-vitro dissolution of the drug at varioustime points for formulations in accordance with the present invention isprovided below:

Time (hours) % Methylphenidate HCl dissolved 0.25  0–45% 1  5–50% 440–90% 8 NLT 60% 12 NLT 80%

In certain preferred embodiments of the present invention, the in-vitrodissolution of the drug at various time points for formulations inaccordance with the present invention is provided below:

Time (hours) % Methylphenidate HCl dissolved 0.25  0–45% 1 10–50% 430–80% 8 NLT 65% 12 NLT 80%

Sustained Release Coatings

In certain preferred embodiments, the drug is incorporated into or ontoa substrate and a sustained release coating is applied thereto. Forexample, the drug may be contained within or on a substrate as follows:(i) incorporated into matrix spheroids (e.g., together with apharmaceutically acceptable spheronizing agent such as microcrystallinecellulose), (ii) coated onto inert pharmaceutically acceptable beads(e.g., nonpareil beads); (iii) incorporated into a normal release tabletcore; or (iv) incorporated into a tablet core which comprises a matrixincluding a sustained release carrier material. Thereafter, a sustainedrelease coating is applied onto substrates such as those mentioned in(i)–(iv) above. The dosage forms of the present invention may optionallycoated with one or more materials suitable for the regulation of releaseor for the protection of the formulation. In one embodiment, coatingsare provided to permit either pH-dependent or pH-independent release,e.g., when exposed to gastrointestinal fluid. A pH-dependent coatingserves to release the drug in desired areas of the gastro-intestinal(GI) tract, e.g., the stomach or small intestine. When a pH-independentcoating is desired, the coating is designed to achieve optimal releaseregardless of pH-changes in the environmental fluid, e.g., the GI tract.It is also possible to formulate compositions which release a portion ofthe dose in one desired area of the GI tract, e.g., the stomach, andrelease the remainder of the dose in another area of the GI tract, e.g.,the small intestine.

Formulations according to the invention that utilize pH-dependentcoatings to obtain formulations may also impart a repeat-action effectwhereby unprotected drug is coated over the enteric coat and is releasedin the stomach, while the remainder, being protected by the entericcoating, is released further down the gastrointestinal tract. Coatingswhich are pH-dependent may be used in accordance with the presentinvention include shellac, cellulose acetate phthalate (CAP), polyvinylacetate phthalate (PVAP), hydroxypropylmethylcellulose phthalate, andmethacrylic acid ester copolymers, zein, and the like.

In certain preferred embodiments, the substrate (e.g., tablet core bead,matrix particle) comprising the drug, is coated with a hydrophobicmaterial selected from (i) an alkylcellulose; (ii) an acrylic polymer;or (iii) mixtures thereof. The coating may be applied in the form of anorganic or aqueous solution or dispersion. The coating may be applied toobtain a weight gain from about 2 to about 25% of the substrate in orderto obtain a desired sustained release profile. Such formulations aredescribed, e.g., in detail in U.S. Pat. Nos. 5,273,760 and 5,286,493,assigned to the Assignee of the present invention and herebyincorporated by reference. The particles are preferably film coated witha material that permits release of the drug so as to achieve, incombination with the other stated properties, a desired in-vitro releaserate and in-vivo plasma levels. The sustained release coatingformulations of the present invention should be capable of producing astrong, continuous film that is smooth and elegant, capable ofsupporting pigments and other coating additives, non-toxic, inert, andtack-free.

Other examples of sustained release formulations and coatings which maybe used in accordance with the present invention include Assignee's U.S.Pat. Nos. 5,324,351; 5,356,467, and 5,472,712, hereby incorporated byreference in their entirety.

Alkylcellulose Polymers

Cellulosic materials and polymers, including alkylcelluloses, providehydrophobic materials well suited for coating the beads according to theinvention. Simply by way of example, one preferred alkylcellulosicpolymer is ethylcellulose, although the artisan will appreciate thatother cellulose and/or alkylcellulose polymers may be readily employed,singly or in any combination, as all or part of a hydrophobic coatingaccording to the invention.

One commercially available aqueous dispersion of ethylcellulose isAquacoat® (FMC Corp., Philadelphia, Pa., U.S.A.). Aquacoat® is preparedby dissolving the ethylcellulose in a water-immiscible organic solventand then emulsifying the same in water in the presence of a surfactantand a stabilizer. After homogenization to generate submicron droplets,the organic solvent is evaporated under vacuum to form a pseudolatex.The plasticizer is not incorporated in the pseudolatex during themanufacturing phase. Thus, prior to using the same as a coating, it isnecessary to intimately mix the Aquacoat® with a suitable plasticizerprior to use.

Another aqueous dispersion of ethylcellulose is commercially availableas Surelease® (Colorcon, Inc., West Point, Pa., U.S.A.). This product isprepared by incorporating plasticizer into the dispersion during themanufacturing process. A hot melt of a polymer, plasticizer (dibutylsebacate), and stabilizer (oleic acid) is prepared as a homogeneousmixture, which is then diluted with an alkaline solution to obtain anaqueous dispersion which can be applied directly onto substrates.

Acrylic Polymers

The hydrophobic material comprising the controlled release coating maycomprise a pharmaceutically acceptable acrylic polymer, including butnot limited to acrylic acid and methacrylic acid copolymers, methylmethacrylate copolymers, ethoxyethyl methacrylates, cyanoethylmethacrylate, poly(acrylic acid), poly(methacrylic acid), methacrylicacid alkylamide copolymer; poly(methyl methacrylate), polymethacrylate,poly(methyl methacrylate) copolymer, polyacrylamide, aminoalkylmethacrylate copolymer, poly(methacrylic acid anhydride), and glycidylmethacrylate copolymers.

In certain preferred embodiments, the acrylic polymer is comprised ofone or more ammonio methacrylate copolymers. Ammonio methacrylatecopolymers are well known in the art, and are described in NF XVII asfully polymerized copolymers of acrylic and methacrylic acid esters witha low content of quaternary ammonium groups.

In order to obtain a desirable dissolution profile, it may be necessaryto incorporate two or more ammonio methacrylate copolymers havingdiffering physical properties, such as different molar ratios of thequaternary ammonium groups to the neutral (meth)acrylic esters.

Certain methacrylic acid ester-type polymers are useful for preparingpH-dependent coatings which may be used in accordance with the presentinvention. For example, there are a family of copolymers synthesizedfrom diethylaminoethyl methacrylate and other neutral methacrylicesters, also known as methacrylic acid copolymer or polymericmethacrylates, commercially available as Eudragit® from Röhm Tech, Inc.There are several different types of Eudragit®. For example, Eudragit® Eis an example of a methacrylic acid copolymer which swells and dissolvesin acidic media. Eudragit® L is a methacrylic acid copolymer which doesnot swell at about pH<5.7 and is soluble at about pH>6. Eudragit® S doesnot swell at about pH<6.5 and is soluble at about pH>7. Eudragit® RL andEudragit® RS are water swellable, and the amount of water absorbed bythese polymers is pH-dependent, however, dosage forms coated withEudragit® RL and RS are pH-independent.

In certain preferred embodiments, the acrylic coating comprises amixture of two acrylic resin lacquers commercially available from RohmPharma under the Tradenames Eudragit® RL30D and Eudragit® RS30D,respectively. Eudragit® RL30D and Eudragit® RS30D are copolymers ofacrylic and methacrylic esters with a low content of quaternary ammoniumgroups, the molar ratio of ammonium groups to the remaining neutral(meth)acrylic esters being 1:20 in Eudragit® RL30D and 1:40 in Eudragit®RS30D. The mean molecular weight is about 150,000. The code designationsRL (high permeability) and RS (low permeability) refer to thepermeability properties of these agents. Eudragit® RL/RS mixtures areinsoluble in water and in digestive fluids. However, coatings formedfrom the same are swellable and permeable in aqueous solutions anddigestive fluids.

The Eudragit® RL/RS dispersions of the present invention may be mixedtogether in any desired ratio in order to ultimately obtain a sustainedrelease formulation having a desirable dissolution profile. Desirablesustained release formulations may be obtained, for instance, from aretardant coating derived from 100% Eudragit® RL, 50% Eudragit® RL and50% Eudragit® RS, and 10% Eudragit® RL: 90% Eudragit® RS. Of course, oneskilled in the art will recognize that other acrylic polymers may alsobe used, such as, for example, Eudragit® L.

Plasticizers

In embodiments of the present invention where the coating comprises anaqueous dispersion of a hydrophobic material such as an alkylcelluloseor an acrylic polymer, the inclusion of an effective amount of aplasticizer in the aqueous dispersion of hydrophobic material willfurther improve the physical properties of the sustained releasecoating. For example, because ethylcellulose has a relatively high glasstransition temperature and does not form flexible films under normalcoating conditions, it is preferable to incorporate a plasticizer intoan ethylcellulose coating containing sustained release coating beforeusing the same as a coating material. Generally, the amount ofplasticizer included in a coating solution is based on the concentrationof the film-former, e.g., most often from about 1 to about 50 percent byweight of the film-former. Concentration of the plasticizer, however,can only be properly determined after careful experimentation with theparticular coating solution and method of application.

Examples of suitable plasticizers for ethylcellulose include waterinsoluble plasticizers such as dibutyl sebacate, diethyl phthalate,triethyl citrate, tributyl citrate, and triacetin, although it ispossible that other water-insoluble plasticizers (such as acetylatedmonoglycerides, phthalate esters, castor oil, etc.) may be used.Triethyl citrate is an especially preferred plasticizer for the aqueousdispersions of ethyl cellulose of the present invention.

Examples of suitable plasticizers for the acrylic polymers of thepresent invention include, but are not limited to citric acid esterssuch as triethyl citrate NF XVI, tributyl citrate, dibutyl phthalate,and possibly 1,2-propylene glycol. Other plasticizers which have provedto be suitable for enhancing the elasticity of the films formed fromacrylic films such as Eudragit® RL/RS lacquer solutions includepolyethylene glycols, propylene glycol, diethyl phthalate, castor oil,and triacetin. Triethyl citrate is an especially preferred plasticizerfor the aqueous dispersions of ethyl cellulose of the present invention.

It has further been found that the addition of a small amount of talcreduces the tendency of the aqueous dispersion to stick duringprocessing, and acts as a polishing agent.

When the aqueous dispersion of hydrophobic material is used to coat asubstrate including the drug, for example, inert pharmaceutical beadssuch as nu pariel 18/20 beads, a plurality of the resultant stabilizedsolid controlled release beads may thereafter be placed in a gelatincapsule in an amount sufficient to provide an effective controlledrelease dose when ingested and contacted by an environmental fluid,e.g., gastric fluid or dissolution media. Alternatively, the substratemay be a tablet core coated with the sustained release coating, andoptionally a further film-forming agent or colorant, such as Opadry®.

In formulations where an aqueous dispersion of an hydrophobic polymersuch as an alkylcellulose is applied to the substrate, it is preferredthat the coated substrate is cured at a temperature above the glasstransition temperature of the plasticized polymer and at a relativehumidity above ambient conditions, until an endpoint is reached at whichthe coated formulation attains a dissolution profile which issubstantially unaffected by exposure to storage conditions, e.g., ofelevated temperature and/or humidity. Generally, in such formulationsthe curing time is about 24 hours or more, and the curing conditions maybe, for example, about 60° C. and 85% relative humidity. Detailedinformation concerning the stabilization of such formulations is setforth in U.S. Pat. Nos. 5,273,760; 5,681,585; and 5,472,712; all ofwhich are hereby incorporated by reference in their entireties.

In formulations where an aqueous dispersion of an acrylic polymer isapplied to the substrate, it is preferred that the coated substrate iscured at a temperature above the glass transition temperature of theplasticized polymer until an endpoint is reached at which the coatedformulation attains a dissolution profile which is substantiallyunaffected by exposure to storage conditions, e.g., of elevatedtemperature and/or humidity. Generally, the curing time is about 24hours or more, and the curing temperature may be, for example, about 45°C. Detailed information concerning the stabilization of suchformulations is set forth in U.S. Pat. Nos. 5,286,493; 5,580,578; and5,639,476; all of which are hereby incorporated by reference in theirentireties.

The sustained release profile of the coated formulations of theinvention-can be altered, for example, by varying the amount ofovercoating with the aqueous dispersion of hydrophobic material,altering the manner in which the plasticizer is added to the aqueousdispersion of hydrophobic material, by varying the amount of plasticizerrelative to hydrophobic material, by the inclusion of additionalingredients or excipients, by altering the method of manufacture, etc.The dissolution profile of the ultimate product may also be modified,for example, by increasing or decreasing the thickness of the retardantcoating.

Spheroids or beads coated with a therapeutically active agent areprepared, e.g., by dissolving the therapeutically active agent in waterand then spraying the solution onto a substrate, for example, nu pariel18/20 beads, using a Wuster insert. Optionally, additional ingredientsare also added prior to coating the beads in order to assist the bindingof the drug to the beads, and/or to color the solution, etc. Forexample, a product which includes hydroxypropylmethylcellulose, etc.with or without colorant (e.g., Opadry®, commercially available fromColorcon, Inc.) may be added to the solution and the solution mixed(e.g., for about 1 hour) prior to application of the same onto thebeads. The resultant coated substrate, in this example beads, may thenbe optionally overcoated with a barrier agent, to separate thetherapeutically active agent from the hydrophobic controlled releasecoating. An example of a suitable barrier agent is one which compriseshydroxypropylmethylcellulose. However, any film-former known in the artmay be used. It is preferred that the barrier agent does not affect thedissolution rate of the final product.

The beads may then be overcoated with an aqueous dispersion of thehydrophobic material. The aqueous dispersion of hydrophobic materialpreferably further includes an effective amount of plasticizer, e.g.triethyl citrate. Pre-formulated aqueous dispersions of ethyl-cellulose,such as Aquacoat® or Surelease®, may be used. If Surelease is used, itis not necessary to separately add a plasticizer. Alternatively,pre-formulated aqueous dispersions of acrylic polymers such as Eudragitcan be used.

The coating solutions of the present invention preferably contain, inaddition to the film-former, plasticizer, and solvent system (i.e.,water), a colorant to provide elegance and product distinction. Colormay be added to the solution of the therapeutically active agentinstead, or in addition to the aqueous dispersion of hydrophobicmaterial. For example, color be added to Aquacoat via the use of alcoholor propylene glycol based color dispersions, milled aluminum lakes andopacifiers such as titanium dioxide by adding color with shear to watersoluble polymer solution and then using low shear to the plasticizedAquacoat. Alternatively, any suitable method of providing color to theformulations of the present invention may be used. Suitable ingredientsfor providing color to the formulation when an aqueous dispersion of anacrylic polymer is used include titanium dioxide and color pigments,such as iron oxide pigments. The incorporation of pigments, may,however, increase the retard effect of the coating.

The plasticized aqueous dispersion of hydrophobic material may beapplied onto the substrate comprising the therapeutically active agentby spraying using any suitable spray equipment known in the art. In apreferred method, a Wurster fluidized-bed system is used in which an airjet, injected from underneath, fluidizes the core material and effectsdrying while the acrylic polymer coating is sprayed on. A sufficientamount of the aqueous dispersion of hydrophobic material to obtain apredetermined sustained release of the therapeutically active agent(i.e., drug) when the coated substrate is exposed to aqueous solutions,e.g. gastric fluid, is preferably applied, taking into account thephysical characteristics of the therapeutically active agent, the mannerof incorporation of the plasticizer, etc. After coating with thehydrophobic material, a further overcoat of a film-former, such asOpadry, is optionally applied to the beads. This overcoat is provided,if at all, in order to substantially reduce agglomeration of the beads.

The release of the drug from the sustained release formulation of thepresent invention can be further influenced, i.e., adjusted to a desiredrate, by the addition of one or more release-modifying agents, or byproviding one or more passageways through the coating. The ratio ofhydrophobic material to water soluble material is determined by, amongother factors, the release rate required and the solubilitycharacteristics of the materials selected.

The release-modifying agents which function as pore-formers may beorganic or inorganic, and include materials that can be dissolved,extracted or leached from the coating in the environment of use. Thepore-formers may comprise one or more hydrophilic materials such ashydroxypropylmethylcellulose.

The sustained release coatings of the present invention can also includeerosion-promoting agents such as starch and gums.

The sustained release coatings of the present invention can also includematerials useful for making microporous lamina in the environment ofuse, such as polycarbonates comprised of linear polyesters of carbonicacid in which carbonate groups reoccur in the polymer chain.

The release-modifying agent may also comprise a semi-permeable polymer.

In certain preferred embodiments, the release-modifying agent isselected from hydroxypropylmethylcellulose, lactose, metal stearates,and mixtures of any of the foregoing.

The sustained release coatings of the present invention may also includean exit means comprising at least one passageway, orifice, or the like.The passageway may be formed by such methods as those disclosed in U.S.Pat. Nos. 3,845,770; 3,916,889; 4,063,064; and 4,088,864 (all of whichare hereby incorporated by reference). The passageway can have any shapesuch as round, triangular, square, elliptical, irregular, etc.

The substrate of the present invention may be prepared by a spheronizingagent together with the active agent ingredient that can be spheronizedto form spheroids. Microcrystalline cellulose is preferred. A suitablemicrocrystalline cellulose is, for example, the material sold as AvicelPH 101 (Trade Mark, FMC Corporation). In such embodiments, in additionto the active ingredients and spheronizing agent, the spheroids may alsocontain a binder. Suitable binders, such as low viscosity, water solublepolymers, will be well known to those skilled in the pharmaceutical art.However, water soluble hydroxy lower alkyl cellulose, such ashydroxypropylcellulose, are preferred. Additionally (or alternatively)the spheroids may contain a water insoluble polymer, especially anacrylic polymer, an acrylic copolymer, such as a methacrylic acid-ethylacrylate copolymer or ethyl cellulose. In such embodiments, thesustained-release coating will generally include a water insolublematerial such as (a) a wax, either alone or in admixture with a fattyalcohol; or (b) shellac or zein.

In a particular preferred embodiment of the invention, thecontrolled/modified release methylphenidate formulation is prepared as amultilayered release (MLR) formulation comprising coated inert beads. Asummary of one method of manufacturing such a formulation is outlined asfollows. First, immediate release (IR) methylphenidate beads areprepared by spraying a solution of methylphenidate in water over sugarbeads in a fluid bed dryer with a drug load of about 8%. The sprayprocess is carried out in a fluid bed dryer, equipped with a Wurstercolumn. A clear overcoat of HPMC is applied using an Qpadry® material(e.g., Opadry® Clear (Formula No: YS-1-7006)), to a weight gain of about1%. Next, a controlled release coating is applied to the IR beads, whichconverts the same into controlled release (CR) beads. This isaccomplished by spraying a solution of Eudragit® RS 30 D, triethylcitrate (plasticizer) and talc (glidant), onto the IR beads. Next, thecoated beads are cured in order to obtain a stabilized release rate ofthe therapeutically active agent. In preferred embodiments of thepresent invention where the CR coating utilizes an acrylic resin tocontrol the release of the drug, the CR beads at this stage aresubjected to oven curing at a temperature above the Tg of theplasticized acrylic polymer of the required time period, the optimumvalues of the temperature and time for the particular formulation beingdetermined experimentally. In certain embodiments of the presentinvention, the stabilized products is obtained via oven curing conductedat a temperature of about 40–50° C. for a time period of about 12 toabout 24 hours or longer. An enteric coating is then applied onto the CRbeads to convert the same into enteric coated CR (ECCR) beads. This isaccomplished by spraying a solution of Eudragit® L 30 D-55 dispersion,triethyl citrate (plasticizer) and talc (glidant) onto the CR beads.Finally, an immediate release coating is applied onto the ECCR beads(referred to as, e.g., an IR Topcoat). This is accomplished by sprayinga solution of methylphenidate in water over EC CR beads.

Results of initial studies show that this formulation is stable underroom temperature (25° C., 60% RH) and accelerated conditions (40° C.,75% RH).

Sustained Release Matrices

In certain preferred embodiments of the present invention, the sustainedrelease formulation comprises a matrix including the drug and asustained release carrier (which may comprise one or more hydrophobicmaterials, such as an alkylcellulose and/or an acrylic polymer aspreviously defined herein). The materials suitable for inclusion in asustained release matrix will depend on the method used to form thematrix.

Suitable materials for inclusion in the sustained release matrices ofthe invention, in addition to the drug, include:

(A) hydrophilic and/or hydrophobic materials, such as gums;alkylcelluloses; cellulose ethers, including hydroxyalkylcelluloses andcarboxyalkylcelluloses; acrylic resins, including all of the acrylicpolymers and copolymers discussed above, and protein derived materials.This list is not meant to be exclusive, and any pharmaceuticallyacceptable hydrophobic material or hydrophilic material which is capableof imparting the desired sustained release profile of the drug is meantto be included herein. The dosage form may comprise, e.g., from about 1%to about 80% by weight of such material.

In certain preferred embodiments of the present invention, thehydrophobic material is a pharmaceutically acceptable acrylic polymer,including but not limited to acrylic acid and methacrylic acidcopolymers, methyl methacrylate, methyl methacrylate copolymers,ethoxy-ethyl methacrylates, cyanoethyl methacrylate, aminoalkylmethacrylate copolymer, poly(acrylic acid), poly(methacrylic acid),methacrylic acid alkylamine copolymer, poly(methyl methacrylate),poly(methacrylic acid)(anhydride), polymethacrylate, polyacrylamide,poly(methacrylic acid anhydride), and glycidyl methacrylate copolymers.In other embodiments, the hydrophobic material is selected frommaterials such as hydroxyalkylcelluloses such ashydroxypropylmethylcellulose and mixtures of the foregoing. In yet otherembodiments, the hydrophobic material is an alkylcellulose.

(B) digestible, long chain (C₈–C₅₀, especially C₁₂–C₄₀), substituted orunsubstituted hydrocarbons, such as fatty acids, fatty alcohols,glyceryl esters of fatty acids, mineral and vegetable oils and naturalor synthetic waxes, polyhydric alcohols, including polyalkylene glycols.The oral dosage form may contain up to 60% (by weight) of such material.In certain embodiments, a combination of two or more hydrocarbonmaterials are included in the matrix formulations. If an additionalhydrocarbon material is included, it is preferably selected from naturaland synthetic waxes, fatty acids, fatty alcohols, and mixtures of thesame.

Preferred hydrocarbons are water-insoluble with more or less pronouncedhydrophilic and/or hydrophobic trends, and have a melting point fromabout 30° C. to about 200° C., preferably from about 45° C. to about 90°C.

For purposes of the present invention, a wax-like substance is definedas any material which is normally solid at room temperature and has amelting point of from about 30° C. to about 100° C. Suitable waxesinclude, for example, beeswax, glycowax, castor wax and carnauba wax.

The aliphatic alcohol may be, for example, lauryl alcohol, myristylalcohol or stearyl, cetyl and/or cetostearyl alcohol. The amount ofaliphatic alcohol, if included in the present oral dosage form, will bedetermined, as above, by the precise rate of drug release required. Incertain embodiments, the oral dosage form contains between 20% and 50%(by wt) aliphatic alcohol. When at least one polyalkylene glycol ispresent in the oral dosage form, then the combined weight of the atleast one aliphatic alcohol and the at least one polyalkylene glycolpreferably constitutes between 20% and 50% (by wt) of the total dosage.

In one embodiment, the ratio of, e.g., the at least one hydroxyalkylcellulose or acrylic resin to the at least one aliphaticalcohol/polyalkylene glycol determines, to a considerable extent, therelease rate of the drug from the formulation.

Suitable polyalkylene glycols include, for example, polypropylene glycolor polyethylene glycol. The number average molecular weight of the atleast one polyalkylene glycol is preferred between 1,000 and 15,000especially between 1,500 and 12,000.

In addition to the above ingredients, a controlled release matrix mayalso contain suitable quantities of other materials, e.g. diluents,lubricants, binders, granulating aids, colorants, flavorants andglidants that are conventional in the pharmaceutical art.

In order to facilitate the preparation of a solid, sustained release,oral dosage form according to this invention, any method of preparing amatrix formulation known to those skilled in the art may be used. Forexample incorporation in the matrix may be effected, for example, by (a)forming granules comprising at least one water soluble hydroxyalkylcellulose and drug or an drug salt; (b) mixing the hydroxyalkylcellulose containing granules with at least one C₁₂–C₃₆ aliphaticalcohol; and (c) optionally, compressing and shaping the granules.Preferably, the granules are formed by wet granulating the hydroxyalkylcellulose/drug with water. In a particularly preferred embodiment ofthis process, the amount of water added during the wet granulation stepis preferably between 1.5 and 5 times, especially between 1.75 and 3.5times, the dry weight of the drug.

In yet other alternative embodiments, a spheronizing agent, togetherwith the active ingredient can be spheronized to form spheroids.Microcrystalline cellulose is preferred. A suitable microcrystallinecellulose is, for example, the material sold as Avicel PH 101 (TradeMark, FMC Corporation). In such embodiments, in addition to the activeingredient and spheronizing agent, the spheroids may also contain abinder. Suitable binders, such as low viscosity, water soluble polymers,will be well known to those skilled in the pharmaceutical art. However,water soluble hydroxy lower alkyl cellulose, such ashydroxypropylcellulose, are preferred. Additionally (or alternatively)the spheroids may contain a water insoluble polymer, especially anacrylic polymer, an acrylic copolymer, such as a methacrylic acid-ethylacrylate copolymer, or ethyl cellulose. In such embodiments, thesustained release coating will generally include a hydrophobic materialsuch as (a) a wax, either alone or in admixture with a fatty alcohol; or(b) shellac or zein.

Melt Extrusion Matrices

In certain preferred embodiments of the present invention, the sustainedrelease matrices also be prepared via melt-granulation or melt-extrusiontechniques. Such formulations are described in U.S. patent applicationSer. No. 08/334,209, filed Nov. 4, 1994 and U.S. patent application Ser.No. 08/833,948, filed Apr. 10, 1997, both of which are herebyincorporated by reference in their entireties. Generally,melt-granulation techniques involve melting a normally solid hydrophobicmaterial, e.g. a wax, and incorporating a powdered drug therein. Toobtain a sustained release dosage form, it may be necessary toincorporate an additional hydrophobic substance, e.g. ethylcellulose ora water-insoluble acrylic polymer, into the molten wax hydrophobicmaterial. Examples of sustained release formulations prepared viamelt-granulation techniques are found in U.S. Pat. No. 4,861,598,assigned to the Assignee of the present invention and herebyincorporated by reference in its entirety.

The additional hydrophobic material may comprise one or morewater-insoluble wax-like thermoplastic substances possibly mixed withone or more wax-like thermoplastic substances being less hydrophobicthan said one or more water-insoluble wax-like substances. In order toachieve constant release, the individual wax-like substances in theformulation should be substantially non-degradable and insoluble ingastrointestinal fluids during the initial release phases. Usefulwater-insoluble wax-like substances may be those with a water-solubilitythat is lower than about 1:5,000 (w/w).

In addition to the above ingredients, a sustained release matrix mayalso contain suitable quantities of other materials, e.g., diluents,lubricants, binders, granulating aids, colorants, flavorants andglidants that are conventional in the pharmaceutical art. The quantitiesof these additional materials will be sufficient to provide the desiredeffect to the desired formulation. In addition to the above ingredients,a sustained release matrix incorporating melt-extruded multiparticulatesmay also contain suitable quantities of other materials, e.g. diluents,lubricants, binders, granulating aids, colorants, flavorants andglidants that are conventional in the pharmaceutical art in amounts upto about 50% by weight of the particulate if desired.

Specific examples of pharmaceutically acceptable carriers and excipientsthat may be used to formulate oral dosage forms are described in theHandbook of Pharmaceutical Excipients, American PharmaceuticalAssociation (1986), incorporated by reference herein.

The preparation of a suitable melt-extruded matrix according to thepresent invention may, for example, include the steps of blending thedrug analgesic (i.e., drug) together with at least one hydrophobicmaterial and preferably the additional hydrophobic material to obtain ahomogeneous mixture. The homogeneous mixture is then heated to atemperature sufficient to at least soften the mixture sufficiently toextrude the same. The resulting homogeneous mixture is then extruded toform strands. The extrudate is preferably cooled and cut intomultiparticulates by any means known in the art. The strands are cooledand cut into multiparticulates. The multiparticulates are then dividedinto unit doses. The extrudate preferably has a diameter of from about0.1 to about 5 mm and provides sustained release of the therapeuticallyactive agent for a time period of from about 8 to about 24 hours. Themultiparticulates may be divided into unit doses via placement into agelatin capsule, or may be compressed into a suitable tablet form.

An optional process for preparing the melt extrusions of the presentinvention includes directly metering into an extruder a hydrophobicmaterial, a therapeutically active agent, and an optional binder;heating the homogenous mixture; extruding the homogenous mixture tothereby form strands; cooling the strands containing the homogeneousmixture; cutting the strands into particles having a size from about 0.1mm to about 12 mm; and dividing said particles into unit doses. In thisaspect of the invention, a relatively continuous manufacturing procedureis realized.

The diameter of the extruder aperture or exit port can also be adjustedto vary the thickness of the extruded strands. Furthermore, the exitpart of the extruder need not be round; it can be oblong, rectangular,etc. The exiting strands can be reduced to particles using a hot wirecutter, guillotine, etc.

The melt extruded multiparticulate system can be, for example, in theform of granules, spheroids or pellets depending upon the extruder exitorifice. For purposes of the present invention, the terms “melt-extrudedmultiparticulate(s)” and “melt-extruded multiparticulate system(s)” and“melt-extruded particles” shall refer to a plurality of units,preferably within a range of similar size and/or shape and containingone or more active agents and one or more excipients, preferablyincluding a hydrophobic material as described herein. In this regard,the melt-extruded multiparticulates will be of a range of from about 0.1to about 12 mm in length and have a diameter of from about 0.1 to about5 mm In addition, it is to be understood that the melt-extrudedmultiparticulates can be any geometrical shape within this size range.Alternatively, the extrudate may simply be cut into desired lengths anddivided into unit doses of the therapeutically active agent without theneed of a spheronization step.

In one preferred embodiment, oral dosage forms are prepared to includean effective amount of melt-extruded multiparticulates within a capsule.For example, a plurality of the melt-extruded multiparticulates may beplaced in a gelatin capsule in an amount sufficient to provide aneffective sustained release dose when ingested and contacted by gastricfluid.

In another preferred embodiment, a suitable amount of themultiparticulate extrudate is compressed into an oral tablet usingconventional tableting equipment using standard techniques. Techniquesand compositions for making tablets (compressed and molded), capsules(hard and soft gelatin) and pills are also described in Remington'sPharmaceutical Sciences, (Arthur Osol, editor), 1553–1593 (1980),incorporated by reference herein.

In yet another preferred embodiment, the extrudate can be shaped intotablets as set forth in U.S. Pat. No. 4,957,681 (Klimesch, et. al.),described in additional detail above and hereby incorporated byreference.

Optionally, the sustained release melt-extruded multiparticulate systemsor tablets can be coated, or the gelatin capsule can be further coated,with a sustained release coating such as the sustained release coatingsdescribed above. Such coatings preferably include a sufficient amount ofhydrophobic material to obtain a weight gain level from about 2 to about30 percent, although the overcoat may be greater depending upon thephysical properties of the particular drug analgesic compound utilizedand the desired release rate, among other things.

The melt-extruded unit dosage forms of the present invention may furtherinclude combinations of melt-extruded multiparticulates containing oneor more of the therapeutically active agents disclosed above beforebeing encapsulated. Furthermore, the unit dosage forms can also includean amount of an immediate release therapeutically active agent forprompt therapeutic effect. The immediate release therapeutically activeagent may be incorporated, e.g., as separate pellets within a gelatincapsule, or may be coated on the surface of the multiparticulates afterpreparation of the dosage forms (e.g., controlled release coating ormatrix-based). The unit dosage forms of the present invention may alsocontain a combination of controlled release beads and matrixmultiparticulates to achieve a desired effect.

The sustained release formulations of the present invention preferablyslowly release the therapeutically active agent, e.g., when ingested andexposed to gastric fluids, and then to intestinal fluids. The sustainedrelease profile of the melt-extruded formulations of the invention canbe altered, for example, by varying the amount of retardant, i.e.,hydrophobic material, by varying the amount of plasticizer relative tohydrophobic material, by the inclusion of additional ingredients orexcipients, by altering the method of manufacture, etc.

In other embodiments of the invention, the melt extruded material isprepared without the inclusion of the therapeutically active agent,which is added thereafter to the extrudate. Such formulations typicallywill have the therapeutically active agent blended together with theextruded matrix material, and then the mixture would be tableted inorder to provide a slow release formulation. Such formulations may beadvantageous, for example, when the therapeutically active agentincluded in the formulation is sensitive to temperatures needed forsoftening the hydrophobic material and/or the retardant material.

The substrates of the present invention may be also be prepared via amelt pelletization technique. In such circumstances, the active drug infinely divided form is combined with a binder (also in particular formand other optional inert ingredients, and thereafter the mixture ispelletized, e.g. by mechanically working the mixture in a high shearmixer to form the pellets (granules, spheres). Thereafter, the pellets(granules, spheres) may be sieved in order to obtain pellets of therequisite size. The binder material is preferably in particulate formand has a melting point above about 40° C. Suitable binder substancesinclude, for example, hydrogenated castor oil, hydrogenated vegetableoil, other hydrogenated fats, fatty acid esters, fatty acid glycerides,and the like.

Proposed strengths of the methylphenidate formulations of the inventionmay be, e.g., 10, 15, 20 and 30 mg. In MLR methylphenidatemultiparticulate formulations of the invention, proposed capsule sizesand fill weights for such dosage strengths are as follows:

Strength Fill Weight Capsule Size 10 mg 100 mg 4 15 mg 150 mg 3 20 mg200 mg 2 30 mg 300 mg 1

In certain preferred embodiments of the present invention, an effectiveamount of the drug in immediate release form is included in the drugformulation. The immediate release form of the drug is included in anamount which is effective to shorten the time to maximum concentrationof the drug in the blood (e.g., plasma), such that time to T_(max) isshortened to a time of, e.g., from about 0.5 to about 2 hours. Byincluding an amount of immediate release drug in the formulation, thetime to onset of action is significantly reduced, and is the same orearlier than that of the reference standard IR treatment (Ritalin IR).

In such embodiments, an effective amount of the drug in immediaterelease form may be coated onto the substrates (e.g., multiparticulatesor tablets) of the present invention. For example, where the extendedrelease of the drug from the formulation is due to a controlled releasecoating, the immediate release layer can be overcoated on top of thecontrolled release coating. On the other hand, the immediate releaselayer may be coated onto the surface of substrates wherein the drug isincorporated in a controlled release matrix. Where a plurality of thesustained release substrates comprising an effective unit dose of thedrug (e.g., multiparticulate systems including pellets, spheres, beadsand the like) are incorporated into a hard gelatin capsule, theimmediate release portion of the drug dose may be incorporated into thegelatin capsule via inclusion of the sufficient amount of immediaterelease drug as a powder or granulate within the capsule. Alternatively,the gelatin capsule itself may be coated with an immediate release layerof the drug. One skilled in the art would recognize still otheralternative manners of incorporating the immediate release drug portioninto the unit dose. Such alternatives are deemed to be encompassed bythe appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples illustrate various aspects of the presentinvention. They are not to be construed to limit the claims in anymanner whatsoever.

EXAMPLE 1 Methylphenidate HCl Immediate Release Beads

TABLE 1 Ingredients % Methylphenidate hydrochloride 15.0 Sugar bead14/18 80.0 Opadry ® clear YS-1-7006 5.0 Water q.s. Total 100.0

-   1. Charge Niro-Aeromatic Strea 1 Fluid Bed Wurster Coater with 14/18    mesh Nupareil® PG (sugar spheres NF).-   2. Coat the beads at 60° C. by spraying a solution of    methylphenidate hydrochloride (12% w/w) and Opadry clear (4% w/w) in    water.-   3. Once the coating is completed, allow the beads to dry at 60° C.    for 2 or 3 minutes.-   4. Cool the beads in a shallow pan at room temperature.-   5. Break agglomerates, if any.-   6. Sift the beads through Tyler 10 mesh sieve (1.77 mm opening) and    then through Tyler 20 mesh sieve (850 micrometer opening) to remove    fines.-   7. Apply top coat to beads by spraying a solution of coloured Opadry    clear solution (4% w/w) to a theoretical weight gain of 1% w/w.    After the completion of the overcoat, the beads are then filled into    hard gelatin capsules at a strength of 20 mg.    Dissolution testing was conducted on the bead filled IR capsules    using USP Apparatus 1 (basket method) in 500 mL of simulated gastric    juice without enzyme, 100 rpm at 37° C. The results are as follows:

TABLE 2 Time (minutes) % Methylphenidate HCl dissolved 10 92.7 20 95.730 97.7 45 98.5The dissolution results as set forth in the above table indicate that98.5% of the methylphenidate hydrochloride was dissolved in 45 minutes.

EXAMPLE 2 Methylphenidate HCl Controlled-Release (CR) Beads with AcrylicPolymer Coating

TABLE 3 Ingredients % Methylphenidate IR beads 86.20 Eudragit ® RS 30 D8.63 Triethyl citrate 1.72 Talc 3.45 Water q.s. Total 100.0The controlled-release coating is manufactured as follows:

-   1. The Eudragit® RS 30 D is plasticized with triethyl citrate and    talc approximately 30 minutes.-   2. A load of the IR beads is charged into a Wurster insert of an    Aeromatic Fluid Bed Dryer with 1 mm spray nozzle and the beads are    coated to a weight gain of −8%.-   3. Upon completion of the coating, the beads are cured for 24 hours    at 40–45° C.    The beads were then filled into hard gelatin capsules at a 20 mg    strength.

Dissolution testing was conducted on the bead filled CR capsules usingthe following USP Apparatus (basket method). The capsules were placedinto 500 mL of simulated gastric juice without enzyme, for first 2 hoursat 100 rpm and 37° C. and then placed into 500 mL simulated intestinalfluid without enzyme for the remainder of the testing period. Theresults are as follows:

TABLE 4 Time (hours) Methylphenidate HCl dissolved 1 6.9 2 16.2 3 26.1 435.7 6 59.8 8 74.7 12 75.4 18 82.5 24 92.8

The dissolution results as set forth in the above table indicate that92.8% of methylphenidate hydrochloride dissolved in 24 hours.

EXAMPLES 3 & 4 Dependence of Release Rate of Methylphenidate HCl fromControlled-Release (CR) Beads on Amount of Acrylic Polymer Coating

By adjusting the amount of Eudragit® RS 30 D applied, the release ratecan be adjusted. This effect is illustrated in Examples 3 and 4 below:

TABLE 5 % Ingredients Example 3 Example 4 Methylphenidate HCl IR 91.294.0 Bead Eudragit ® RS 30 D 5.8 3.9 Triethyl citrate 1.0 0.7 Talc 2.01.4 Water — — Total 100.0 100.0

The method of manufacturing the controlled-release beads in Examples 3and 4 is similar to the method described under Example 2, by varying theproportion of beads and Eudragit® RS 30 D.

The cured beads were filled into hard gelatin capsules at a strength of20 mg.

The dissolution results, conducted under conditions identical to thosefound under Example 2, are shown below:

TABLE 6 % Methylphenidate HCl Time dissolved (hours) Example 3 Example 41 18.7 49.5 2 35.1 73.3 3 49.0 81.5 4 60.6 85.2 6 75.7 90.4 8 77.3 90.712 82.1 92.8

The dissolution results as set forth in the above table, indicate that82.1% and 92.8% respectively of methylphenidate hydrochloride isdissolved in 12 hours. However, the release of drug from Example 4 wassignificantly faster at time points 1, 2, 3, 4, 6 and 8 hours.

EXAMPLE 5 Enteric Coated (EC) Coated Release (CR) Beads—EC•CR Beads

TABLE 7 Ingredients % Methylphenidate CR beads 83.2 Eudragit ® L 30 D559.9 Triethyl citrate 2.0 Talc 4.9 Water q.s. Total 100.0The enteric coating procedure is described below:

-   1. The Eudragit® L 30 D 55 is plasticized with triethyl citrate and    talc approximately 30 minutes.-   2. A load of the methylphenidate CR beads is charged into a Wurster    insert of an Aeromatic Fluid Bed Dryer with 1 nm spray nozzle and    the beads are coated to a weight gain of ˜9%.-   3. Upon completion of the coating, the beads are cured for 18 hours    at 40° C.-   4. The cured beads are then sieved through Tyler 10 mesh (1.7 mm    opening) and Tyler 20 mesh (850 micrometer opening) sieves to remove    any fines.    The beads were then filled onto hard gelatin capsules at a 20 mg    strength.

Dissolution testing was conducted on the bead filled CR filled capsulesusing USP Apparatus 1 (basket method) 500 mL at 100 rpm and 37° C. usingSGF without enzyme for the first 2 hours and SIF without enzyme for therest of the testing period. Results are shown below:

TABLE 8 % Methylphenidate Time HCl dissolved (hours) Lot 1 Lot 2 Lot 3 10.4 1.0 2.0 2 2.2 5.4 7.4 3 18.8 27.8 61.3 4 36.7 48.3 87.0 6 59.5 75.598.8 8 76.9 90.1 100.0 12 82.3 99.6 —

The dissolution results as set forth in the above table indicate thatvery little drug is dissolved in gastric juice after enteric coating andthat the dissolution profile of the CR beads has been modified.

EXAMPLE 6 Formulations for Clinical Trials

Examples 6A, 6B and 6C below set forth the formulations developed andtested in clinical studies.

EXAMPLE 6A IR•EC•CR Beads Immediate Release (IR) Coating of EntericCoated Controlled-Release (EC•CR) Methylphenidate Beads

The (IR•EC•CR Beads) formulation, hereinafter referred to as Formulation1, is a capsule containing multi-layer release beads which have bothimmediate release and controlled release components. It is made up of acontrolled release bead which is enteric coated to delay dissolutionuntil after gastric emptying. The enteric coated controlled release beadhas an immediate release topcoat to provide an initial rate ofabsorption equal to or greater than Ritalin® IR immediate releasetablets. The immediate release component represent 40% of the total doseper bead and the controlled release component represents 60%.

TABLE 9 Ingredients % Enteric coated Controlled Release 91.4Methylphenidate HCl beads Methylphenidate hydrochloride USP 6.5 Opadry ®clear YS-1-7006 2.1 Water q.s. Total 100.0

The application of an immediate release coat on the top of EntericCoated CR beads is described below:

-   1. Dissolve methylphenidate HCl USP and Opadry in water with    stirring.-   2. Load EC•CR beads into a Wurster insert of an Aeromatic Fluid Bed    Dryer.-   3. Spray the beads with the coating solution using a 1 mm spray    nozzle at a temperature of not more than 50° C.-   4. Once the coating is completed, cool the beads at room temperature    and pass through Tyler sieves 10 and 20 mesh to remove fines.

The beads were then filled into a hard gelatin capsule to a 20 mgstrength.

Dissolution testing was conducted on the bead filled capsules ofFormulation 1 using USP Apparatus 1 (basket method) 100 rpm, 500 mL at37° C.—simulated gastric juice without enzyme 1st and 2nd hours; 3rdhour onwards simulated intestinal fluid without enzyme.

The results are as follows:

TABLE 10 Time (hours) % Methylphenidate HCl dissolved  5 minutes 37.0 10minutes 38.0 15 minutes 39.0 30 minutes 40.0 60 minutes 40.0 2 40.1 351.4 4 61.0 6 75.6 8 87.0 12  87.5The dissolution results as set forth in the above table indicate a rapidonset on dissolution, followed by prolonged action.

EXAMPLE 6B IR+EC•CR Blend Combination of Immediate ReleaseMethylphenidate Beads (IR) and Enteric Coated Controlled-Release (EC•CR)Methylphenidate Beads

The enteric-coated controlled release beads (EC•CR) beads described inExample 5 may be mixed with the immediate release (IR) beads describedin Example 1 in varying proportions and placed in capsules to obtain thefinal blended dosage form, (IR+EC•CR Blend), hereinafter referred to asFormulation 2. Formulation 2 was designed to provide a faster rate ofabsorption of the controlled release portion than Formulation 1. Theimmediate release component represents 35% of the total dose per capsuleand the controlled release component represents 65%.

Dissolution testing was performed and the comparative results are shownin Table 11 below.

EXAMPLE 6C IR•CR Beads Immediate Release (IR) Coating ofControlled-Release (CR) Methylphenidate Beads

The IR•CR Beads formulation, hereinafter referred to as Formulation 3,is a capsule containing single beads made up of an immediate releasetopcoat and a controlled release core, and is designed to provide anintermediate rate of absorption of the controlled release portionbetween that of the controlled release formulations of Formulations 1and 2. The immediate release component represents 30% of the total doseper bead and the controlled release component represents 70%.

The immediate release topcoat is applied to CR beads as described inExample 6A for Formulation 1.

The dissolution profiles of Formulations 1–3 and Ritalin® SR, used as acomparator, are shown in Table 11 below. Hours 1 and 2 are in 500 ml ofsimulated gastric fluid. Simulated intestinal fluid (500 ml) is usedfrom the third hour onwards. The results of the dissolution testingconfirmed the anticipated in vitro dissolution profile.

TABLE 11 Comparative Dissolution of Formulations Formulation FormulationTime (Hours) Ritalin SR Formulation 1 2 3 10 min 21.4 38.0 32.0 28.6 30min 31.4 40.0 36.7 34.0 1 45.7 40.0 38.2 40.5 2 62.3 40.1 40.4 57.6 375.8 51.4 68.1 70.6 4 79.5 61.0 86.4 79.5 6 88.0 75.6 95.4 89.6 8 90.787.0 96.2 92.7 12  91.3 87.5 97.0 93.1

EXAMPLE 7 Four Way Comparison of Single Dose Formulation 1 (Fed andFasted) with Two Doses of Ritalin IR (Fed and Fasted)

The bioavailability of Methylphenidate MLR capsules was investigated ina four-way blind study which compared the Formulation 120 mg singledosage formulation under fed and fasted conditions with two doses (4hours apart) of Ritalin® IR.

Healthy male volunteers were given a single dose of 20 mg Formulation 1or two doses of immediate release methylphenidate 10 mg administeredfour hours apart under both fed and fasting conditions (n=12). “Fed”conditions indicates the test formulation was given to the subjectsafter they had eaten a high-fat breakfast. Following an overnight fastof at least 10.0 hours, each of the normal, healthy, non-smoking, malesubjects were given the following treatment according to Williams design4 treatment randomization scheme.

Treatment 1: Test Product: methylphenidate controlled-release,Formulation 1, 20 mg capsule, the morning under fasting conditions.

Treatment 2: Reference Product: methylphenidate immediate-release,Ritalin® (Novartis), 10 mg tablet in the morning and 4 hours later,under fasting conditions.

Treatment 3: Test Product: methylphenidate controlled-release,Formulation 1, 20 mg capsule, administered 5 minutes after a high fatbreakfast.

Treatment 4. Reference Product: methylphenidate immediate-release,Ritalin® (Novartis), 10 mg tablet in the morning and 4 hours later,administered 5 minutes after a high fat breakfast.

There was a seven day washout period between the study periods. Duringeach study period, blood samples (1×5 mL each) were taken from eachsubject within one hour prior to dosing and at 0.250, 0.500, 0.750,1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, 5.00, 6.00, 7.00, 8.00,10.0, 12.0, 16.0, 24.0 hours post-dose for the Formulation 1 and atpre-dose, 0.250, 0.500, 0.750, 1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00,4.50, 5.00, 6.00, 7.00, 8.00, 10.0, 12.0, 16.0, 24.0 hours post-dose forthe Ritalin® IR. Plasma was harvested from each blood sample and storedin a −20° C. freezer until assayed for plasma methylphenidateconcentration. Assay of plasma methylphenidate concentrations wasperformed using gas chromatography/mass spectrometry (GC/MS).

The mean plasma concentrations, standard deviations and coefficients ofvariation are shown as a function of time in Tables 12 and 13, forfasting and fed conditions, respectively.

This data is presented graphically in FIGS. 1–4. FIG. 1 presents themean plasma concentration versus time for Formulation 1 and Ritalin®under fasting conditions. FIG. 2 presents the mean plasma concentrationversus time for Formulation 1 and Ritalin® under fed conditions. FIG. 3presents the mean plasma concentration versus time for Formulation 1under fed and fasting conditions. FIG. 4 presents the mean plasmaconcentration versus time for Ritalin® under fed and fasting conditions.

TABLE 12 Mean Plasma Concentrations (pg/mL) of Methylphenidate:Formulation 1 and Ritalin ® IR (fasting) Formulation 1 Ritalin SampleTime Concen- Concen- (h) tration SD (±) CV (%) tration SD (±) CV (%)0.000 0.00 0.00 — 0.00 0.00 — 0.250 0.00 0.00 — 0.00 0.00 — 0.500 817.53801.84 98.08 883.96 686.65 77.68 0.750 2268.79 1128.12 49.72 2485.74828.38 33.33 1.00 3108.79 756.66 24.34 3468.74 1172.28 33.80 1.503597.88 740.36 20.58 4388.04 998.86 22.76 2.00 3675.60 1315.29 35.784289.39 1144.40 26.68 2.50 3469.81 882.62 25.44 4121.37 1014.57 24.523.00 3573.56 1031.61 28.87 3528.56 863.25 24.46 3.50 3637.01 1008.7327.74 3020.93 716.36 23.71 4.00 3604.03 1071.59 29.73 2747.91 698.9525.44 4.50 3494.44 1069.13 30.60 2958.49 799.89 27.04 5.00 3446.411069.50 31.03 4394.22 1603.40 36.49 5.50 — — — 5525.84 1766.58 31.976.00 3421.13 1166.25 34.09 5927.06 1955.99 33.00 6.50 — — — 5528.411758.49 31.81 7.00 3422.32 958.42 28.00 4860.45 1482.24 30.50 8.003338.59 724.49 21.70 3795.34 1500.79 39.54 10.0 2858.42 612.21 21.422223.48 926.11 41.65 12.0 2073.97 536.08 25.85 1334.71 523.37 39.21 16.01180.67 502.11 42.53 455.86 287.79 63.13 24.0 275.87 201.51 73.04 55.1099.99 181.46

TABLE 13 Mean Plasma Concentrations (pg/mL) of Methylphenidate:Formulation 1 and Ritalin ® IR (fed) Formulation 1 Ritalin Sample TimeConcen- Concen- (h) tration SD (±) CV (%) tration SD (±) CV (%) 0.0000.00 0.00 — 0.00 0.00 — 0.250 0.00 0.00 — 53.12 133.84 251.95 0.500291.66 271.58 93.11 1256.61 1602.66 127.54 0.750 910.22 653.80 71.832984.60 3406.53 114.14 1.00 1580.66 983.13 62.20 3400.39 2301.87 67.691.50 2760.68 797.24 28.88 5205.16 1882.17 36.16 2.00 3098.73 874.4928.22 5146.55 1617.43 31.43 2.50 3655.68 982.31 26.87 5157.11 1227.9923.81 3.00 3625.88 797.55 22.00 4546.61 932.94 20.52 3.50 3717.71 951.5825.60 4184.34 1080.71 25.83 4.00 3650.63 875.97 23.99 3652.57 1023.2228.01 4.50 3627.41 835.40 23.03 3811.27 1103.83 28.96 5.00 3430.14783.72 22.85 5158.45 1714.53 33.24 5.50 — — — 5982.98 1618.65 27.05 6.003418.03 937.07 27.42 6228.81 1591.64 25.55 6.50 — — — 6054.32 1919.9531.71 7.00 4218.94 775.86 18.39 5538.57 1741.02 31.43 8.00 4679.671126.52 24.07 4350.90 1611.95 37.05 10.0 3858.58 1045.56 27.10 2577.66896.59 34.78 12.0 2610.98 902.53 34.57 1521.52 611.54 40.19 16.0 1372.86737.71 53.74 577.90 334.26 57.84 24.0 334.79 306.63 91.59 94.23 144.99153.86Experimental Results

Pharmacokinetic parameters were calculated based on the data from thefour-way study. AUC_(0-t) (pg·h/mL), AUC_(0-inf) (pg·h/mL), AUC_(t/inf)(%), C_(max) (pg/mL), T_(max) (hours), T_(1/2 el) (hours), K_(el)(hour⁻¹), TLIN (hours) and LQCT (hours) were calculated as describedbelow.

For purposes of the present invention, the following terms are meant tohave the following meanings:

Analysis of Pharmacokinetic Data and Statistical Analysis

-   AUC_(0-t) Area under the concentration-time curve from time zero to    the time of the last non-zero concentration (this corresponds to the    area under the concentration-time curve, over the dosing interval of    the test formulation for both controlled-release and    immediate-release formulations)-   AUC_(0-inf) Area under the concentration-time curve from time zero    to infinity-   C.I. Confidence interval-   CV Coefficient of variation-   C_(max) Maximum observed concentration-   K_(el) Elimination rate constant-   LQCT The last quantifiable concentration time-   SD Standard deviation-   TLIN The time point where log-linear elimination begins-   T_(1/2 el) Time for observed C_(max)-   Sampling Time Time post dose of plasma collection based on    parameters to be studied-   Scheduled Time The predetermined (clock) time at which the samples    are to be taken-   Actual time The exact (clock) time at which the sample was taken

Time deviations during sampling for drugs with a T_(max)≦4 hours weretreated as follows: between 0 and 6 hours post dose, the sampling timewas used in the statistical analysis if the delay between the actual andscheduled time of blood collection was <10%. Above 6 hours post dose,the sampling time was used in the statistical analysis if the delaybetween the actual and scheduled time of plasma collection was <15%.When sampling times were used when previously described acceptancecriteria, the corrected sampling items were used when performingpharmacokinetic parameters calculations. Sampling times are present inconcentration tables and graphs of statistical report.

The mean, standard deviation (SD), and coefficient of variation (CV)were calculated for plasma concentrations of methylphenidate for eachsampling time and treatment. As well, the mean, SD, and CV werecalculated for the AUC_(0-t) (pg·h/mL), AUC_(0-inf) (pg·h/mL), C_(max)(pg/mL), T_(max) (hours), T_(1/2 el) (hours), K_(el) (hour⁻¹), TLIN(hours) and LQCT (hours). The calculation of these pharmacokineticparameters is explained below.

Areas Under the Concentration-Time Curves

AUC_(0-t) was calculated using the linear trapezoidal rule.

The AUC_(0-t) was derived where t is the time (t) of the last measurable(non-zero) concentration (C_(t)) for each treatment.

The AUC_(0-inf) was calculated as:

${AUC}_{0 - t} + \frac{C_{t}}{K_{el}}$Where C_(t)=the last non-zero concentration for that treatment,AUC_(0-t)=the AUC from time zero to the time of the last non-zeroconcentration for that treatment and K_(el)=the elimination rateconstant.Maximum Observed Concentration and Time of Observed Peak Concentration

The maximum observed concentration, C_(max), and the observed time toreach peak concentration, T_(max), was determined for each subject andfor each treatment.

Half-Life and Elimination Rate Constant

To calculate the elimination rate constant (K_(el)), linear regressionanalyses were performed on the natural log (Ln) of plasma concentrationvalues (y) versus time (x). Calculations were made between a time pointwhere log-linear elimination phase begins (LQCT) occurred. The K_(el)was taken as the slope multiplied by (−1) and the apparent half-life(T_(1/2 el)) as 0.693/K_(el).

TLIN and LQCT

TLIN, the time point where log-linear elimination begins, and LQCT, thelast quantifiable concentration time were determined for each subjectand for each treatment.

Percent Drug Absorbed

Percent drug absorbed was calculated at each sampling time (t) byModified Wagner-Nelson's method, as implemented in Kinetica software,version 2.0.1 according to the following formula:

$\frac{C_{t} + \left( {K_{el} \times {AUC}_{0 - t}} \right)}{\left( {K_{el} \times {AUC}_{0 - \inf}} \right)} \times 100$

All ANOVAs were performed with the SAS General Linear Models Procedure(GLM). For all analyses, effects were considered statisticallysignificant if the probability associated with ‘F’ was less than 0.050.Based on the pairwise comparisons of the ln-transformed AUC_(0-t),AUC_(0-inf) and C_(max) data, the relative ratios of the geometricmeans, calculated according to the formulation “e^((X-Y))×100”, as wellas the 90% geometric confidence intervals were determined.

Results

The plasma concentration of unchanged methylphenidate followingadministration of the controlled release formulation Formulation 1reached the maximum concentration (C_(max)) at a mean of 3.27 hoursunder fasting conditions and 7.29 hours under fed conditions reflectinga biphasic absorption profile. The plasma concentration of unchangedmethylphenidate following administration of two doses of the immediaterelease formulation (Ritalin® IR) reached the maximum concentration(C_(max)) at 5.96 hours under fasting conditions and 3.54 hours underfed conditions. When the determination of C_(max) was restricted to thefirst dose of immediate release methylphenidate, the T_(max) was 1.71hours under fasting conditions and 1.63 hours under fed conditions.

The complete pharmacokinetic parameters of controlled releasemethylphenidate 20 mg Formulation 1 and immediate releasemethylphenidate 10 mg (Ritalin® IR) under fed and fasted conditions aresummarized in Tables 14 and 15 below.

TABLE 14 Pharmacokinetic Parameters for Formulation 1 Formulation 1(fasting) Formulation 1 (fed) Parameters Mean ± SD CV (%) Mean ± SD CV(%) AUC_(0–t) (pg · h/mL) 48493.80 ± 13430.27 27.69 54686.38 ± 15118.6627.65 AUC_(0–inf) (pg · h/mL) 51213.86 ± 13260.14 26.59 57931.47 ±16762.54 28.94 C_(max) (pg/mL) 4410.25 ± 1188.68 26.95 4879.37 ± 1027.8521.07 T_(max) (h) 3.27 ± 2.54 77.64 7.29 ± 1.29 17.65 K_(el) (h⁻¹)0.1672 ± 0.0339 20.25 0.1812 ± 0.0392 21.65 T_(1/2el)(h) 4.32 ± 0.9622.18 4.06 ± 1.25 30.91

TABLE 15 Pharmacokinetic Parameters for Ritalin ® IR RITALIN ® (fasting)RITALIN ® (fed) Parameters Mean ± SD CV (%) Mean ± SD CV (%) AUC_(0–t)(pg · h/mL) 44644.22 ± 13806.82 30.93 52781.49 ± 15194.94 28.79AUC_(0–inf) (pg · h/mL) 46466.23 ± 14012.73 30.16 54783.17 ± 15311.0827.95 C_(max) (pg/mL) 6536.04 ± 1669.29 25.54 7571.74 ± 1534.58 20.27T_(max) (h) 5.96 ± 0.54 9.09 3.54 ± 2.42 68.43 K_(el) (h⁻¹) 0.2481 ±0.0550 22.17 0.2449 ± 0.0719 29.37 T_(1/2el)(h) 2.93 ± 0.71 24.10 3.08 ±0.96 31.26

The results of the ANOVA and Duncan's Multiple Range Test performed onthe ln-transformed AUC_(0-t) data show a statistically significantdifference between treatments for this parameter. According to Dunican'sMultiple Range Test, the AUC_(0-t) of treatment 1 was significantlydifferent from the AUC_(0-t) of treatments 2 and 3. However, Duncan'sMultiple Range Test did not detect statistically significant differencesbetween treatments 3 and 4 for this parameter. The statistical analysesperformed on the data are summarized in Table 16 below:

TABLE 16 AUC_(0–t) (pg · h/mL) TRT 1 vs. TRT 2 TRT 3 vs. TRT 4 TRT 1 vs.TRT 3 Ratio 109.90% 104.08% 88.65% 90% 102.59% to  97.15% to 82.75% toGeometric 117.74% 111.50% 94.97% C.I.

The results of the ANOVA and Duncan's Multiple Range Test performed onthe ln-transformed AUC_(0-inf) data show a statistically significantdifference between treatments for this parameter. According to Duncan'sMultiple Range Test, the AUC_(0-inf) of treatment 1 was significantlydifferent from the AUC_(0-inf) of treatments 2 and 3. However, Duncan'sMultiple Range Test did not detect statistically significant differencesbetween treatments 3 and 4 for this parameter. The statistical analysesperformed on the data are summarized below in Table 17:

TABLE 17 AUC_(0–inf) (pg · h/mL) TRT 1 vs. TRT 2 TRT 3 vs. TRT 4 TRT 1vs. TRT 3 Ratio 111.65% 105.86% 88.85% 90% 104.09% to  98.70% to 82.84%to Geometric 119.95% 113.55% 95.30% C.I.

The results of the ANOVA and Duncan's Multiple Range Test performed onthe ln-transformed C_(max) data show a statistically significantdifference between treatments for this parameter. According to Duncan'sMultiple Range Test, the C_(max) of treatment 1 was not significantlydifferent from the C_(max) of treatment 3. However, Duncan's MultipleRange Test detected statistically significant differences for C_(max)when comparing treatments 1 and 2 and treatments 3 and 4. Thestatistical analyses performed on the data are summarized below in Table18:

TABLE 18 C_(max) (pg/mL) TRT 1 vs. TRT 2 TRT 3 vs. TRT 4 TRT 1 vs. TRT 3Ratio 67.48% 64.38%  89.37% 90% 60.28% to 57.51% to  79.83% to Geometric75.54% 72.07% 100.04% C.I.

The ANOVA and Duncan's Multiple Range Test performed on the T_(max) datadetected a statistically significant difference between treatments forthis parameter. Duncan's Multiple Range Test detected statisticallysignificant differences between treatments 1 and 2, treatments 3 and 4,and treatments 1 and 3 for this parameter.

The ANOVA and Duncan's Multiple Range Test performed on the T_(1/2 el)data detected a statistically significant difference between treatmentsfor this parameter. Duncan's Multiple Range Test detected nostatistically significant differences between treatments 1 and 3 forT_(1/2 el). However, Duncan's Multiple Range Test detected statisticallysignificant differences between treatments 1 and 2 and treatments 3 and4 for this parameter.

The results of the ANOVA and Duncan's Multiple Range Test performed onthe K_(el) data show a statistically significant difference betweentreatments for this parameter. Statistically significant differenceswere detected by Duncan's Multiple Range Test between treatments 1 and 2and treatments 3 and 4, but not for treatments 1 and 0.3.

Summary and Analysis

The AUC and C_(max) ratios of controlled release methylphenidate 20 mgFormulation 1 under fed and fasted conditions are summarized in Table 19below. A comparison of the AUC and C_(max) ratios for immediate releasemethylphenidate 10 mg (Ritalin® IR) and Formulation 1 under fastingconditions are summarized in Table 20 below. Table 21 shows thecomparative ratios for immediate release methylphenidate 10 mg (Ritalin®IR) and Formulation 1 under fed conditions.

Treatment 1 (Formulation 1, Fasting) Versus Treatment 3 (Formulation 1,Fed)

The ANOVAs detected statistically significant differences betweentreatments for ln-transformed AUC_(0-t), AUC_(0-inf) and C_(max), anduntransformed T_(max), K_(el), T_(1/2 el). Duncan's Multiple Range Testdetected statistically significant differences between treatments 1 and3 for ln-transformed AUC_(0-t) and AUC_(0-inf) and untransformedT_(max). However, Duncan's Multiple Range Test detected no statisticallysignificant differences between treatments for ln-transformed C_(max)and untransformed K_(el) and T_(1/2 el). All formulation ratios, as wellas 90% geometric confidence intervals of the relative mean AUC_(0-t),AUC_(0-inf) and C_(max) of the test product (Formulation 1, fasting) toreference product (Formulation 1, fed) were found to be within 80 to125%. This is summarized in Table 19 below:

TABLE 19 Formulation 1 (Fed) vs. Formulation 1 (Fast) AUC_(0–t)AUC_(0–inf) C_(max) Ratio¹ 112.80% 112.54% 111.90% 90% 105.29%–120.84%104.93%–120.71% 99.96%–125.27% Geometric C.I.² ¹Calculated usinggeometric means according to the formula:e^([Formulation 1 (fed)−Formulation 1 (fasting)]) × 100 ²90% GeometricConfidence Interval using ln-transformed dataTreatment 1 (Formulation 1, Fasting) Versus Treatment 2 (Ritalin®,Fasting)

The ANOVAs detected statistically significant differences betweentreatments for ln-transformed AUC_(0-t), AUC_(0-inf) and C_(max), anduntransformed T_(max), K_(el), T_(1/2el). Duncan's Multiple Range Testdetected statistically significant differences between treatments 1 and2 for all parameters. With the exception of C_(max), all formulationratios as well as 90% geometric confidence intervals of the relativemean AUC_(0-t) and AUC_(0-inf) of the test product (Formulation 1) toreference product (Ritalin) were found to be within the 80 to 125%. Thisis summarized in Table 20 below:

TABLE 20 Formulation 1 (Fast) vs Ritalin ® (Fast) AUC_(0–t) AUC_(0–inf)C_(max) Ratio¹ 109.90% 111.65% 67.48% 90% 102.59%– 104.09%– 60.28%–Geometric C.I.² 117.74% 119.75% 75.54% ¹Calculated using geometric meansaccording to the formula: e^([Formulation 1 (fast)−Ritalin IR (fast)]) ×100 ²90% Geometric Confidence Interval using log-transformed dataTreatment 3 (Formulation 1, Fed) Versus Treatment 4 (Ritalin®, Fed)

The ANOVAs detected statistically significant differences betweentreatments for ln-transformed AUC_(0-t), AUC_(0-inf) and C_(max), anduntransformed T_(max), K_(el), T_(1/2el). Duncan's Multiple Range Testdetected statistically significant differences between treatments 3 and4 for all parameters with the exception of ln-transformed AUC_(0-t) andAUC_(0-inf). With the exception of C_(max), all formulation ratios, aswell as 90% geometric confidence intervals of the relative meanAUC_(0-t) and AUC_(0-inf) of the test product (Formulation 1) toreference product (Ritalin) were found to be within the 80% to 125%.This is summarized in Table 21 below:

TABLE 21 Formulation 1 (Fed) vs. Ritalin ® IR (Fed) AUC_(0–t)AUC_(0–inf) C_(max) Ratio¹ 104.08% 105.86% 64.38% 90%  97.15%–  98.70%–57.51%– Geometric C.I.² 111.50% 113.55% 72.07% ¹Calculated usinggeometric means according to the formula:e^([Formulation 1 (fed)−Ritalin IR (fed)]) × 100 ²90% GeometricConfidence Interval using log-transformed dataConclusions

Review of individual plasma MPH time curves indicates the following:

Plasma MPH concentrations at 12 hours were higher on Formulation 1 thanon Ritalin IR in all subjects, under both fed and fasted conditions.

A biphasic profile was apparent under fasted conditions in 7–10/12subjects and in 8–10/12 under fed conditions. The mean curve showing astable plateau under fasted conditions is therefore not fullyrepresentative of the individual profiles. The enteric coat thereforegave rise to a biphasic profile in some subjects even under fastedconditions.

Under fasted conditions the apparent rate of rise of plasma MPH wasequivalent to, or faster than, that of Ritalin IR in 8/12subjects underfasted conditions and 4–5/12 subjects under fed conditions. The meancurves which demonstrate an equivalent rate of rise under fastedconditions and a slower rise under fed conditions were therefore largelyreflective of the individual profiles.

The bioavailability of Formulation 1 relative to Ritalin IR wasacceptable under both fed and fasted conditions (Relative AUC_(inf) 106%and 112%). There was an increase in AUC of both Formulation 1 andRitalin when given with food (13.1% and 17.9% respectively).

Formulation 1 had a more prolonged mean plasma MPH concentration timeprofile than two doses of Ritalin IR. An across study comparisonindicates that Formulation 1 also has a more prolonged profile thanRitalin SR.

Under fasted conditions Formulation 1 had a mean initial rate of rise ofplasma MPH that is similar to Ritalin IR and a relatively flat plateauuntil 8 hours post-dose.

Under fed conditions, the initial rise in plasma NTH from Formulation 1was slower than under fasted conditions and the plateau showed abiphasic profile. This was consistent with predictions that the entericcoat would delay release of the controlled release component and thatthis delay would be longer under fed conditions (allowing the initialplasma concentration peak, due to the IR component, to fall prior to thestart of release from the controlled release component).

Formulation 1 results in both a fast initial rate of rise of plasmamethylphenidate concentration, and a prolonged duration. Thetransformation from a prolonged plateau profile under fasted conditionsto a biphasic profile under fed conditions, is as predicted. Formulation1 therefore has the potential to meet the dual objectives of rapid onsetand prolonged duration that are considered desirable characteristics ofa controlled release methylphenidate formulation for the treatment ofADD/ADHD.

An initial pilot bioavailability study completed in adult healthyvolunteers has confirmed that a single 20 mg dose of this formulationhas an equivalent extent of absorption to two doses of immediate releasemethylphenidate (10 mg) given 4 hours apart. Maximal plasmaconcentrations with the controlled release formulation are similar tothose attained with the first dose of immediate release methylphenidateand from approximately 10 hours post-dose, are higher than thosefollowing the second dose of immediate release methylphenidate.

The results indicate the potential for a single morning dose of thisformulation to produce clinical effects that are at least equivalent tothose of two doses of immediate-release methylphenidate given atbreakfast and lunchtime, with a duration of action that may reduce theneed for a third dose of immediate release methylphenidate later in theday.

EXAMPLE 8 Five-Way Comparison of Single Dose Formulation 2 (Fed andFasted), Single Dose Formulation 3 (Fed and Fasted) and Single DoseRitalin SR (Fasted)

A five-way blind study was conducted which compared a single dose ofFormulation 2, 20 mg, both fed and fasted, a single dose of Formulation3, 20 mg, both fed and fasted, and Ritalin SR 20 mg single dose fasted.According to the published literature and anecdotal comments fromphysicians, Ritalin SR is used in less than 20% of methylphenidatetreated patients.

Twelve healthy male volunteers were given a single dose of either 20 mgFormulation 2 or Formulation 3 administered four hours apart under bothfed and fasting conditions (n=12), or slow-release 20 mg methylphenidate(Ritalin SR) under fasting conditions. “Fed” conditions indicates thetest formulation was given to the subjects after they had eaten ahigh-fat breakfast. Following an overnight fast of at least 10.0 hours,each of the normal, healthy, non-smoking, male subjects were given thefollowing treatments according to Williams design 5 treatmentrandomization scheme.

Treatment 1: Test Product: methylphenidate controlled-release,Formulation 2, 20 mg capsule, in the morning under fasting conditions.

Treatment 2: Test Product: methylphenidate controlled-release,Formulation 2, 20 mg capsule, in the morning, under fed conditions.

Treatment 3: Test Product: methylphenidate controlled-release,Formulation 3, 20 mg capsule, under fasting conditions.

Treatment 4: Test Product: methylphenidate controlled-release,Formulation 3, 20 mg capsule, under fed conditions.

Treatment 5: Reference Product: methylphenidate slow-release 20 mgtablet Ritalin SR (Novartis) under fasting conditions.

There was a seven day washout period between the study periods. Duringeach study period, blood samples (1×5 mL each) were taken from eachsubject within one hour prior to dosing and at 0.250, 0.500, 0.750,1.00, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, 5.00, 6.00, 7.00, 8.00,10.0, 12.0, 16.0, 24.0 hours post-dose. Plasma was harvested from eachblood sample and stored in a −20 C freezer until assayed for plasmamethylphenidate concentration.

The data is presented graphically in FIGS. 5–8. FIG. 5 presents the meanplasma concentration versus time for Formulation 2 under fasting and fedconditions and Ritalin® under fasting conditions. FIG. 6 presents themean plasma concentration versus time for Formulation 3 under fastingand fed conditions and Ritalin® under fasting conditions. FIG. 7presents the mean plasma concentration versus time for Formulations 2and 3 under fasting conditions. FIG. 8 presents the mean plasmaconcentration versus time for Formulations 2 and 3 under fed conditions.

The complete pharmacokinetic parameters of controlled releasemethylphenidate 20 mg (Formulation 2 and 3) under fed and fastingconditions, and for slow release methylphenidate 20 mg (Ritalin® SR)under fasting conditions are summarized in Tables 22–24 below.

TABLE 22 Pharmacokinetic Parameters for Formulation 2 Treatment 1,Fasting Treatment 2, Fed Parameters Means ± SD CV (%) Mean ± SD CV (%)AUC_(0–t) (pg · h/mL) 48190.73 ± 11668.71 24.21 53452.63 ± 12820.3923.98 AUC_(0–inf) (pg · h/mL) 49787.07 ± 12053.23 24.21 55690.49 ±12691.52 22.79 C_(max) (pg · h/mL)  7498.57 ± 1968.38 26.25  6879.09 ±1486.53 21.61 T_(max) (h)   3.63 ± 0.57 15.70   6.42 ± 1.08 16.89 K_(el)(h⁻¹)  0.2391 ± 0.0428 17.91  0.2321 ± 0.0342 14.75 T_(1/2) (h)   3.00 ±0.64 21.32   3.05 ± 0.48 15.74

TABLE 23 Pharmacokinetic Parameters for Formulation 3 Treatment 3,Fasting Treatment 4, Fed Parameters Means ± SD CV (%) Mean ± SD CV (%)AUC_(0–t) (pg · h/mL) 48057.06 ± 14743.87 30.68 54128.75 ± 14787.9427.32 AUC_(0–inf) (pg · h/mL) 49984.68 ± 14873.03 29.76 56315.66 ±14779.59 26.24 C_(max) (pg · h/mL)  6080.97 ± 2048.60 33.69  6959.07 ±1559.34 22.41 T_(max) (h)   3.46 ± 0.89 25.76   4.42 ± 0.56 12.62 K_(el)(h⁻¹)  0.2009 ± 0.0468 23.32  0.2057 ± 0.0390 18.97 T_(1/2) (h)   3.65 ±0.97 26.52   3.49 ± 0.70 20.01

TABLE 24 Pharmacokinetic Parameters for Ritalin SR ® Parameters Mean ±SD CV (%) AUC_(0–t) (pg · h/mL) 47404.51 ± 12754.66 26.91 AUC_(0–inf)(pg · h/mL) 49252.17 ± 12841.52 26.07 C_(max) (pg/mL)  6783.09 ± 1496.6522.06 T_(max) (h)   3.50 ± 0.43 12.18 K_(el) (h⁻¹)  0.2282 ± 0.032014.01 T_(1/2el) (h)   3.10 ± 0.47 15.14

The results of the ANOVA and Duncan's Multiple Range Test performed onthe ln-transformed C_(max) data show a statistically significantdifference between treatments for this parameter. According to Duncan'sMultiple Range Test, the C_(max) of treatment 3 was significantlydifferent from the C_(max) of treatments 4 and 5. However, Duncan'sMultiple Range Test did not detect statistically significant differencesbetween treatments for C_(max) when comparing treatment 1 vs. treatment2 or treatment 1 vs treatment 5. The statistical analyses performed onthe data are summarized in Table 25 below:

TABLE 25 C_(max) (pg/mL) TRT 1 vs. TRT 3 vs. TRT 1 vs. TRT 3 vs. TRT 2TRT 4 TRT 5 TRT 5 Ratio 103.73% 84.78% 109.25% 87.40% 90% Geometric 98.94% to 78.59% to 101.28% to 81.05% to C.I. 115.14% 91.45% 117.85%94.26%

The ANOVA and Duncan's Multiple Range Test performed on theln-transformed T_(max) data detected a statistically significantdifference between treatments for this parameter. Duncan's MultipleRange Test detected statistically significant differences betweentreatments 1 and 2, and treatments 3 and 4 for this parameter. Duncan'sMultiple Range Test did not detect statistically significant differencesbetween treatments for T_(max) a when comparing treatments 1 vs. 3 ortreatments 3 vs. 5.

The ANOVA performed on the T_(1/2 el) data detected a statisticallysignificant difference between treatments for this parameter. Duncan'sMultiple Range Test detected no statistically significant differencesbetween treatments 1 and 2, treatments 3 and 4, and treatments 1 and 5for T_(1/2 el). However, Duncan's Multiple Range Test detectedstatistically significant differences between treatments 3 and 5 forthis parameter.

The ANOVA performed on the K_(el) data show a statistically significantdifference between treatments for this parameter. Statisticallysignificant differences were not detected by Duncan's Multiple RangeTest, between treatments for K_(el) when comparing treatments 1 and 2,treatments 3 and 4, or treatments 1 and 5. However, Duncan's MultipleRange Test detected statistically significant differences betweentreatments 3 and 5 for this parameter.

The ANOVA and Duncan's Multiple Range Test performed on theln-transformed AUC_(0-t) data show a statistically significantdifference between treatments for this parameter. According to Duncan'sMultiple Range Test, the AUC_(0-t) of treatments 1 and 3 wassignificantly different from the AUC_(0-t) of treatments 2 and 4respectively. However, Duncan's Multiple Range Test did not detectstatistically significant differences between treatments for AUC_(0-t)when comparing treatment 1 vs treatment 5, or treatment 3 vs treatment5. The statistical analyses performed on the data are summarized belowin Table 26:

TABLE 26 AUC_(0–t) (pg · h/mL) Treatment Treatment Treatment Treatment 1vs. 3 vs. 1 vs. 3 vs. Treatment 2 Treatment 4 Treatment 5 Treatment 5Ratio 89.21% 88.23% 101.82% 100.63% 90% Geometric 84.03% to 83.10% to 95.91% to  94.81% to C.I. 94.71% 93.67% 108.10% 106.81%

The ANOVA and Duncan's Multiple Range Test performed on theln-transformed AUC_(0-inf) data show a statistically significantdifference between treatments for this parameter. According to Duncan'sMultiple Range Test, the AUC_(0-inf) of treatments 1 and 3 wassignificantly different from the AUC_(0-inf) of treatments 2 and 4respectively. However, Duncan's Multiple Range Test did not detectstatistically significant differences between treatments for AUC_(0-inf)when comparing treatment 1 vs treatment 3, or treatment 3 vs treatment5. The statistical analyses performed on the data are summarized belowin Table 27:

TABLE 27 AUC_(0–int) (pg · h/mL) TRT 1 vs. TRT 3 vs. TRT 1 vs. TRT 3 vs.TRT 2 TRT 4 TRT 5 TRT 5 Ratio 88.33% 88.14% 101.14% 100.82% 90%Geometric 83.50% to 83.32% to  95.61% to  95.33% to C.I. 93.44% 93.24%106.99% 106.63%Treatment 1 (Formulation 2, Fasting) vs. Treatment 2 (Formulation 2,Fed)

The ANOVAs detected statistically significant differences between fedand fasting conditions, treatments 1 and 2, for the ln-transformedAUC_(0-t), AUC_(0-inf) and C_(max) and untransformed T_(max), T_(1/2el)and K_(el). Duncan's Multiple Range Test detected statisticallysignificant differences between treatments 1 and 2 for ln-transformedAUC_(0-t) and AUC_(0-inf) and untransformed T_(max). However, Duncan'sMultiple Range Test detected no statistically significant differencesbetween treatments for ln-transformed C_(max) and untransformedT_(1/2el) and K_(el). All formulation ratios, as well as 90% geometricconfidence intervals of the relative mean AUC_(0-t), AUC_(0-inf) andC_(max) were found to be within the 80% to 125%, as is shown in Table 28below. Thus, it appears that food increases the extent of absorption ofmethylphenidate for Formulation 2. However, this food effect was lessthan 20% on average.

TABLE 28 Formulation 2, Fed versus Fasting AUC_(0–t) AUC_(0–inf) C_(max)Ratio¹ 112.09% 113.21% 93.69% 90% 105.58% to 107.03% to 86.85% to101.07% Geometric C.I.² 119.00% 119.76% ¹Calculated using geometricmeans according to the formula:e^((Formulation 2 (Fed)−Formulation 2 (Fasting))) × 100 ²90% GeometricConfidence Interval using ln-transformed dataTreatment 3 (Formulation 3, Fasting) vs. Treatment 4 (Formulation 3,Fed)

The ANOVAs detected statistically significant differences betweentreatments for ln-transformed AUC_(0-t), AUC_(0-inf) and C_(max) anduntransformed T_(max), T_(1/2el) and K_(el). Duncan's Multiple RangeTest detected statistically significant differences between treatments 3and 4 for ln-transformed AUC_(0-t), AUC_(0-inf) and C_(max) anduntransformed T_(max). However, Duncan's Multiple Range Test detected nostatistically significant differences between treatments foruntransformed T_(1/2el) and K_(el). With the exception of lower 90%geometric confidence interval for C_(max), all formulation ratios, aswell as 90% geometric confidence intervals of the relative meanAUC_(0-t), AUC_(0-inf) and C_(max) were found to be within the 80% to125%, as is shown in Table 29 below. Thus, it appears that foodincreases the extent of absorption of methylphenidate for Formulation 3.However, this food effect was less than 20% on average.

TABLE 29 Formulation 3, Fed versus Fasting AUC_(0–t) AUC_(0–inf) C_(max)Ratio¹ 113.35% 113.45% 117.96% 90% 106.76% to 107.25% to 120.01% 109.35%to Geometric 120.33% 127.25% C.I.² ¹Calculated using geometric meansaccording to the formula:e^((Formulation 3 (fed)−Formulation 3 (Fasting))) × 100 ²90% GeometricConfidence Interval using ln-transformed dataTreatment 1 (Formulation 2, Fasting) vs. Treatment 5 (Ritalin SR®,Fasting)

The ANOVAs detected statistically significant differences betweentreatments for ln-transformed AUC_(0-t), AUC_(0-inf) and C_(max) anduntransformed T_(max), T_(1/2el) and K_(el). Duncan's Multiple RangeTest detected no statistically significant differences betweentreatments 1 and 5 for all parameters. All formulation ratios, as wellas 90% geometric confidence intervals of the relative mean AUC_(0-t),AUC_(0-inf) and C_(max) of the test to reference product were found tobe within the 80% to 125%, as shown in Table 30 below. Thus, Formulation2 is bioequivalent to the reference product Ritalin SR® under fastingconditions.

TABLE 30 Formulation 2 (Fasting) versus Ritalin SR (Fasting) AUC_(0–t)AUC_(0–inf) C_(max) Ratio¹ 101.82% 101.14% 106.99% 90%  95.91% to 95.61% to 101.28 to Geometric C.I.² 108.10% 106.99% 117.85% ¹Calculatedusing geometric means according to the formula:e^((Formulation 2 (fast)−Ritalin SR (Fast))) × 100 ²90% GeometricConfidence Interval using ln-transformed dataTreatment 3 (Formulation 3, Fasting) vs. Treatment 5 (Ritalin SR®,Fasting)

The ANOVAs detected statistically significant differences betweentreatments for ln-transformed AUC_(0-t), AUC_(0-inf) and C_(max) anduntransformed T_(max), T_(1/2el) and K_(el). Duncan's Multiple RangeTest detected statistically significant differences between treatments 3and 5 for ln-transformed C_(max) and untransformed T_(1/2el) and K_(el).However, Duncan's Multiple Range Test detected no statisticallysignificant differences between treatments for ln-transformed AUC_(0-t)and AUC_(0-inf) and untransformed T_(max). All formulation ratios, aswell as 90% geometric confidence intervals of the relative meanAUC_(0-t), AUC_(0-inf) and C_(max) of the test to reference product werefound to be within the 80% to 125%, as shown in Table 31 below. Thus,Formulation 3 is bioequivalent to the reference product Ritalin SR®under fasting conditions.

TABLE 31 Formulation 3 (Fasting) versus Ritalin SR (Fasting) AUC_(0–t)AUC_(0–inf) C_(max) Ratio¹ 101.63% 100.82% 87.40% 90%  94.81% to  95.33%to 81.05 to Geometric C.I.² 106.81% 106.63% 94.26% ¹Calculated usinggeometric means according to the formula:e^((Formulation (fast)−Ritalin SR (Fast))) × 100 ²90% GeometricConfidence Interval using ln-transformed dataConclusions

The bioavailability of Formulation 2 relative to Ritalin SR® isacceptable under fasted conditions (Relative AUC_(inf) 101%—Fedconditions not tested).

The bioavailability of Ritalin SR® under fasted conditions is similar tothat of Ritalin® IR, as discussed in Example 7 (AUC_(inf) 29.2 vs. 46.5ng.h/mL, respectively). Literature data which indicates that Ritalin® IRand SR are absorbed at equivalent rates suggests that comparisonsbetween the studies presented in Examples 7 and 8 are reasonable.

Bioavailability of Formulations 1 and 2 are similar under fasted and fedconditions (fasted: 49.8 vs. 51.2 ng.h/mL; fed: 55.7 vs. 57.9 ng.h/mL).

From the mean curves of Formulation 2 and Ritalin SR®, the initial rateof rise of plasma MPH concentration is slightly faster for Formulation 2compared to Ritalin SR®. Under fed conditions, the rate of rise ofplasma MPH with Formulation 2 decreased and T_(max) was delayed incomparison to both Formulation 2 fasted and Ritalin SR® fasted.

Bioavailability of Formulation 3 relative to Ritalin SR® is acceptableunder fasted conditions (Relative AUC_(inf) 100.8%—fed conditions nottested).

Bioavailability of Formulations 1 and 3 are similar under fasted and fedconditions (fasted: 50.0 versus 51.2 ng/hmL; fed: 56.3 versus 57.9ng·h/mL). Note also that Formulations 2 and 3 have almost identical AUCvalues.

From the mean curves for Formulation 3 and Ritalin SR®, the initial rateof rise of plasma MPH concentrations is slightly faster for Formulation3 compared to Ritalin SR®.

In contrast to Formulation 2, the effect of food on the initial rate ofconcentration rise is minimal. Since Formulation 3 does not contain anenteric coat, this suggests that food slows the initial release from theIR component of formulations that contain an enteric coat, both when theenteric coat is part of the same bead (underneath the IR coat in thecase of Formulation 1) and when it is in a separate bead (as forFormulation 2).

Also in contrast to Formulation 2, the T_(max) of the mean curve ofFormulation 3 occurs at a similar time to that of Ritalin SR® under fedand fasted conditions. For Formulation 2 (and Formulation 1) the T_(max)of the second absorption phase under fed conditions is substantiallydelayed relative to Ritalin SR®.

Conclusions

EXAMPLES 7 AND 8

-   1. Formulation 1 has both a fast initial rate of rise, at least    under fasted conditions and a prolonged duration. The transformation    from a prolonged plateau profile under fasted conditions to a    biphasic profile under fed conditions, is as predicted. Since these    conditions represent the extremes of “food stress”, one might    predict that administration in association with normal meals and    times would provide an intermediate profile. It is also possible    that gastric emptying in children on a normal meal schedule will be    faster than in adults fed a high fat meal—this will tend to make the    second absorption phase occur earlier and produce lower    concentrations from 12 hours onwards. Formulation 1 therefore meets    the dual objectives of rapid onset and prolonged duration.-   2. Formulation 2 is also very similar to Ritalin SR® under fasted    conditions but shows a delayed peak under fed conditions such that    plasma MPH concentrations are higher than Ritalin SR® (fasted) from    6 hours post dose onwards. The controlled release component in    Formulation 2 is faster releasing than the one in Formulation 1 and    plasma MPH concentrations are lower for Formulation 2 from about 10    hours post dose.-   3. Overall, Formulation 3 (non-enteric coated) has a profile very    similar to Ritalin SR® under both fed and fasted conditions. The IR    component of Formulation 3 provides some increase in initial    absorption rate relative to Ritalin SR® under fasted conditions.    Since concentrations later in the day are similar for the two    formulations, this confirms the concept that a fast initial rise and    higher concentrations later in the day are not possible at the same    dose, unless a delay is introduced into the release of a component    of the total dose.

EXAMPLE 9

Example 9 is directed to another embodiment of the invention wherein aformulation is prepared which provides both rapid initial onset ofeffect and prolonged duration, and which provides a peak concentrationwhich is not lower than Ritalin IR, while providing a prolonged durationwhich is not too long and which does not cause insomnia at night. Anideal target plasma drug concentration profile is shown in FIG. 9, whichis a plot of Ritalin IR versus Ritalin SR versus Formulation 1(described above in Example 7) versus the “target” formulation ofExample 9.

Assuming first order elimination of methylphenidate in human, the firstorder elimination rate constant was estimated from the linear terminalslope of plasma methylphenidate concentration curve (as plotted inlog-linear paper) following oral administration of Ritalin IR. Theabsorption profile of Formulation 1 described above can be obtainedfollowing deconvolution calculation of the plasma drug concentrationprofile of the same using the Wagner-Nelsen Method (“Fundamentals ofClinical Pharmacokinetics” by John G. Wagner, Drug IntelligencePublications, Inc. 1975, page 174). The in-vitro drug dissolutionprofile correlates well with the in-vivo absorption profile, as shown inFIG. 10. This correlation indicates that the in-vitro dissolution methodcan be used to predict in-vivo drug absorption.

To obtain a target absorption/dissolution profile, assuming first orderelimination of methylphenidate in human, the first order eliminationrate constant was estimated from the linear terminal slope of the plasmamethylphenidate concentration curve (as plotted in log-linear paper)following oral administration of Ritalin IR, via the Wagner-NelsenMethod. The target absorption profile is depicted in FIG. 11. Based onthe established in-vitro/in-vivo correlation as shown in FIG. 10,assuming a similar drug release mechanism is utilized, this in-vivoabsorption curve can be taken as the target dissolution profile.

EXAMPLE 10

In Example 10, a methylphenidate formulation in accordance with thepresent invention is prepared utilizing a melt extrusion granulation(MEG) technique. The ingredients are set forth in the following Table32.

TABLE 32 Ingredient mg/tablet Methylphenidate HCl 15.0 Eudragit RSPO25.0 Stearyl Alcohol 25.0 Eudragit L 100-55 5.0 Avicel PH 102 30.0 Talc2.0 Magnesium Stearate 1.0 103Method of Manufacture:

The Methylphenidate HCl, Eudragit RSPO, Stearyl Alcohol, EudragitL100-55 and Avicel are blended. The powder blend is fed into a turnscrew melt extruder. The heating zones are set to 80° C. and screw speedat 30 rpm, and the powder is fed through the extruder at the elevatedtemperature, and is extruded as warm strands through a die plate withholes of 1 mm. The extruded strands are cooled on the conveyor belt. Thecooled strands are then broken into smaller pieces. The broken strandsare then milled into a granulation using a Fitzmill. The granulation isthen blended with the talc and magnesium stearate and compressed intotablets using a tabletting machine.

The expected dissolution of both these tablets, using USP basketapparatus 1 with a paddle speed of 100 rpm in 500 ml SGF at pH 1.2 fortwo hours followed by 500 ml phosphate buffer at pH 5.8 is set forth inTable 33:

TABLE 33 In-Vitro Dissolution Target Hour % Dissolved % Dissolved 1 3131 3 61 58 8 89 98

EXAMPLE 11

In Example 11, a methylphenidate formulation in accordance with thepresent invention is prepared utilizing the melt extrusion granulation(MEG) technique as set forth in Example 10. The ingredients are setforth in Table 34.

TABLE 34 Ingredient mg/tablet Methylphenidate HCl 15.0 Eudragit RSPO25.0 Stearyl Alcohol 15.0 Eudragit L 100-55 5.0 Avicel PH 102 30.0Polyethylene glycol 8000 10.0 Talc 2.0 Magnesium Stearate 1.0 103

The expected dissolution of both these tablets, using USP basketapparatus 1 with a paddle speed of 100 rpm in 500 ml SGF at pH 1.2 fortwo hours followed by 500 ml phosphate buffer at pH 5.8 is set forth inTable 35:

TABLE 35 Target Hour % Dissolved % Dissolved 1 30 31 3 59 58 8 90 98

EXAMPLE 12

In Example 12, another method of producing controlled releaseMethylphenidate HCl tablets in accordance with the present invention isutilized, via a direct compression technique. The ingredients of Example12 are set forth in Table 36 below:

TABLE 36 Ingredient mg/tablet Methylphenidate HCl 15.0 Lactose DT 15.0Methocel 67.0 Talc 2.0 Magnesium Stearate 1.0 100Method of Manufacture:

The ingredients are blended. The blended material is compressed intotablets. When these tablets were tested for dissolution using the samemethodology noted above, the results were as set forth in Table 37below:

TABLE 37 Target Hour % Dissolved % Dissolved 1 33 31 3 71 58 8 98 98

EXAMPLE 13

In Example 13, the method of producing controlled releaseMethylphenidate HCl tablets in accordance with Example 12 is utilized,via a direct compression technique to produce another formulation. Theingredients of Example 13 are set forth in Table 38 below:

TABLE 38 Ingredient mg/tablet Methylphenidate HCl 15.0 Lactose DT 15.0Eudragit L 100-55 15.0 Methocel 52.0 Talc 2.0 Magnesium Stearate 1.0 100When the tablets were tested for dissolution using the same methodologynoted above, the results were as set forth in Table 39 below:

TABLE 39 Target Hour % Dissolved % Dissolved 1 37 31 3 67 58 8 87 98

The examples provided above are not meant to be exclusive. Many othervariations of the present invention would be obvious to those skilled inthe art, and are contemplated to be within the scope of the appendedclaims.

1. An oral dosage form comprising an effective amount of methylphenidateor a pharmaceutically acceptable salt thereof, wherein a portion of themethylphenidate or pharmaceutically acceptable salt thereof is inimmediate release form and a portion of the methylphenidate orpharmaceutically acceptable salt thereof is in controlled release form,the controlled release form comprising a substrate comprising about 60%to about 70% of the methylphenidate or a pharmaceutically acceptablesalt thereof and at least one pH dependent release modifying coating,wherein the pH dependent release modifying coating is applied to obtaina weight gain from about 2 to about 25% of the substrate, theformulation providing a time to maximum plasma concentration at about0.5 to about 4 hours after oral administration, a peak plasmaconcentration from about 3 ng/ml to about 6.5 ng/ml per 20 mg dose ofmethylphenidate contained in the oral dosage form, wherein the peakconcentration is from about 1.0 to about 2.0 times the plasmaconcentration of methylphenidate provided by the formulation at about 9hours after oral administration, wherein the formulation provides anin-vitro dissolution as follows: Time % Methylphenidate (hours) HCldissolved 0.25  0–45% 1  5–50% 4 40–90% 8 NLT 60% 12 NLT 80%

and wherein the duration of effect provided by the methylphenidatecontained in the formulation falls below effective plasma concentrationsat about 8 to about 12 hours after oral administration, wherein about30% to about 40% of the methylphenidate or pharmaceutically acceptablesalt thereof is in immediate release form.
 2. The oral dosage form ofclaim 1, wherein the oral dosage form provides a time to maximum plasmaconcentration at about 0.5 to about 2 hours after oral administration.3. The oral dosage form of claim 2, wherein the peak plasmaconcentration is from about 1.0 to about 1.7 times the plasmaconcentration of methylphenidate provided by the formulation at about 9hours after oral administration.
 4. The oral dosage form of claim 3,wherein the duration of effect provided by the methylphenidate containedin the oral dosage form falls below effective plasma concentrations atabout 8 to about 10 hours after oral administration.
 5. The oral dosageform of claim 1, which provides a “square wave” plasma profile asdepicted by Formulation
 1. 6. The oral dosage form of claim 1, whichprovides an in-vitro dissolution as follows: Time % Methylphenidate(hours) HCl dissolved 0.25  0–45% 1 10–50% 4 30–80% 8 NLT 65% 12 NLT 80%


7. The oral dosage form of claim 1, wherein the pH dependent releasemodifying coating is selected from the group consisting of shellac,cellulose acetate phthalate, polyvinyl acetate phthalate,hydroxypropylmethylcellulose phthalate, a pH dependent methacrylic acidester copolymer and zein.
 8. The oral dosage form of claim 7, whereinthe pH dependent coating is a pH dependent methacrylic acid estercopolymer.
 9. The oral dosage form of claim 1, wherein the substratecomprises methylphenidate or pharmaceutically acceptable salt thereofcoated onto inert beads.
 10. The oral dosage form of claim 9, whereinthe coated inert beads are overcoated with at least a portion of the pHdependent release modifying coating.